SlideShare a Scribd company logo
3 
DATABASE AND DATABASE 
MANAGEMENT SYSTEMS 
The database is now the underlying framework of the information 
system and has fundamentally changed the way many companies and 
individuals work. In today's technology-intensive economy, most 
organizations around the world- whether they are for - profit, not -for-profit, 
educational or governmental - could not stay competitive or achieve 
their goals without database management systems. Databases touch all 
aspects of our lives (in fact, the database is now such an integral part of 
our day-to-day life that often we're not aware we are using one). Users of 
a database store crucial information - from customers names and suppliers 
prices to sales history and procurement records - update that information 
and make it readily available to whoever needs it. People who work with 
databases are responsible for many of the benefits that computers have 
offered all kinds of organizations. 
These are some examples of Database Applications: 
• Banking: all transactions 
• Airlines: reservations, schedules 
• Universities: registration, grades 
• Sales: customers, products, purchases 
• Manufacturing: production, inventory, orders, supply chain 
• Human resources: employee records, salaries, tax deductions 
FILE-BASED APPROACH 
In the early days, database applications were built on top of file 
systems. That's the traditional way to use computers to back information 
systems: to store data in files and process them by means of dedicated 
programs. The file is a named collection of data regarding similar entities 
(objects, facts, events). 
Drawbacks of using file systems to store data: 
• Data redundancy and inconsistency: multiple file formats, duplication 
of information in different files 
• Difficulty in accessing data: need to write a new program to carry out 
each new task 
• Data isolation : multiple files and formats
• Integrity problems : Integrity constraints become part of program 
4 
code, hard to add new constraints or change existing ones 
• Atomicity of updates: failures may leave database in an inconsistent 
state with partial updates carried out (E.g. transfer of funds from one 
account to another should either complete or not happen at all) 
• Concurrent access by multiple users : concurrent accessed needed for 
performance, uncontrolled concurrent accesses can lead to 
inconsistencies (E.g. two people reading a balance and updating it at 
the same time) 
• Security problems 
These disadvantages were especially pronounced in first and 
second-generation application systems. In third-generation systems, a 
number of powerful support packages and tools have been introduced to 
minimize some of the disadvantages. This software support provides data 
dictionaries, high-level programming languages. However, even with 
these facilities, there remain the fundamental deficiencies of file 
processing systems: redundant data, low sharing of data, lack of standards 
and control, and low productivity. To overcome these disadvantages, a 
new approach emerges in the years 70, the data base approach discussed in 
the following section. 
THE DATABASE APPROACH 
The database approach represents a different concept in 
information resource management. Data are viewed as an important, 
shared resource that must be managed like any other asset, such as people, 
materials, equipment and money. The data base concept is rooted in an 
attitude of sharing common data resources, releasing control of those data 
resources to a common responsible authority, and cooperating in the 
maintenance of those shared data resources. 
The database 
A database consists of a shared collection of logically related data 
(and a description of this data), designed to meet the information needs 
of an organization. The database system provides the organization with 
centralized control of its data. Such a situation contrasts sharply with that 
found in an enterprise without a database system, where typically each 
application has its own private files, so that the data is widely dispersed 
and might thus be difficult to control in any systematic way.
The database is a single, possibly large repository of data, which 
can be used simultaneously by many departments and users. All data that 
is required by these users is integrated with the minimum amount of 
duplication. And, importantly, the database is normally not owned by any 
one department or user but is a shared corporate resource. 
Technically, the database approach differs from the file approach 
by the following features: 
• permanent links are established between files to materialize real life 
interactions. From here, the technical definition is derived: Database 
is a named collection of interrelated files, shared by more users. 
• data descriptions (logical records of each file) are stored on magnetic 
support (not in programs but in data files or close). As well as holding 
the organization's operational data, the database also hold a description 
of this data. For this reason, a database is also defined as a self-describing 
collection of integrated records. The description of data 
(the meta-data) is known as the system catalog or data dictionary. It is 
the self-describing nature of a database that provides what's known as 
data independence. This means that the programs consist only on 
algorithms that are no more data dependent (we can use the same 
program for more data descriptions) and they use the data description 
in common. 
5 
Program Program 
Data description Algorithm 
Algorithm 
Data Description 
Data Data 
File approach Data base approach 
Fig. 2.1 File and database approaches 
The concept of centralized control implies there will be some 
identifiable person who has this central responsibility for the data. That 
person is the data administrator (DA). It is the data administrator’s job to 
decide what data should be stored in the database in the first place, and to 
establish policies for maintaining and dealing with that data once it has
been stored. The technical person responsible for implementing the data 
administrator’s decisions is the database administrator (DBA). 
6 
Data base management system (DBMS) 
The DBMS is a software system that enables users to define, create 
and maintain the database and also provides controlled access to the 
database. So, the DBMS is the software that interacts with the users, 
application programs and the database. 
A database management system (DBMS) is the software used to 
specify the logical organization for a database and access it. 
DBMS provides an environment that is both convenient and 
efficient to use. 
Application programs 
Users interact with the database through a number of application 
programs that are used to create and maintain the database and to generate 
information. These programs can be conventional batch applications or, 
more typically nowadays, they will be online applications. The application 
programs may be written in some programming language or in some 
higher-level fourth-generation language. 
An application program is a computer program that interacts 
with the database by issuing an appropriate request to the DBMS. 
Views 
A DBMS provides a facility known as a view mechanism, which 
allow each user to have his or her own customized view of the database, 
where a view is some subset of the database. 
A view is a virtual table that does not necessarily exist in the 
database but is generated by the DBMS from the underlying base 
tables whenever it's accessed. 
A view is usually defined as a query that operates on the base 
tables to produce another virtual table. As well as reducing complexity by 
letting users see the data in the way they want to see it, views have several 
other benefits: 
- Views provide a level of security. Views can set up to exclude 
data that some users should not see. 
- Views provide a mechanism to customize the appearance of the 
database.
- A view can present a consistent, unchanging picture of the 
structure of the database, even if the underlying database is 
changed. 
Components of the DBMS environment 
We can identify five major components in the DBMS environment: 
1. Hardware - the computer systems that the DBMS and the application 
programs run on. This can change from a single PC, to a single 
mainframe, to a network of computers. 
2. Software - the DBMS software and the application programs, together 
with the operating system, including network software if the DBMS is 
being used over a network. 
3. Data and data descriptions (meta-data) - the data acts like a bridge 
between the hardware and software components and the human 
components. 
4. Procedures - the instructions and rules that govern the design and use 
7 
of the database. 
5. People - In the database environment, human jobs are more specific: 
some users deal only with data retrieving (end users), some with 
developing new information system (application programmers) and 
some must manage the complex data base environment (data 
administrator and database administrator). Also, there are other 
specialists, like database designers (software professionals who 
specify information, content and create database systems), Web-application 
developers (create Web pages and devise means for 
processing information content through the Web) or Web-site 
designers.
8 
. 
End Users DBMS 
group 
FMS 
Programmers 
Operating System 
Database Administrator BIOS 
Database 
Data dictionary 
and directory 
Fig 2.2 Software environment in database approach 
All data handling (storing, updating or retrieving) is done only by 
the DBMS. Some database uses the File Management System to store, 
update and retrieve data in files visible from the Operating system (Dbase, 
Fox, Paradox). Modern DBMS like Microsoft Access and Oracle don’t use 
the File Management System, they had their own routines of storing data 
in tables enclosed in a container seen as a unique file by the Operating 
System. Sometimes, the DBMS replace totally the FMS and sometimes 
the DBMS is embedded in the Operating System. 
DBMS architectures 
Before the advent of the Web, generally a DBMS would be divided in two 
parts: 
• a client program that handles the main business and data processing 
logic and interfaces with the user; 
• a server program (sometimes called the DBMS engine) that manages 
and controls access to the database. 
This is known as a two-tier client-server architecture.
In the mid -1990s, as applications became more complex and potentially 
could be developed to hundreds and thousands of end-users, the client side 
of this architecture gave rise to two problems: 
ü A "fat" client, requiring considerable resources on the client's 
9 
computer to run effectively (disk space, RAM and CPU power). 
ü A significant client-side administration overhead. 
By 1995, a new variation of the traditional two-tier client-server model 
appeared to solve these problems, called three-tier client-server 
architecture. This new architecture proposed three layers, each 
potentially running on a different platform: 
• The user interface layer, which runs on the end-user's computer (the 
client). 
• The business logic and data processing layer - a middle layer which 
runs on a server and is often called the application server. One 
application server is designed to serve multiple clients. 
• A DBMS, which stores the data required by the middle layer. This tier 
may run on a separate server called the database server. 
The three-tier design has many advantages over the traditional two-tier 
design, such as: 
ü A "thin" client, which requires less expensive hardware. 
ü Simplified application maintenance, as a result of centralizing the 
business logic for many end-users into a single application server. 
ü Added modularity, which makes it easier to modify or replace one tier 
without affecting the other tiers. 
ü Easier load balancing, as a result of separating the core business logic 
from the database functions. A Transaction Processing Monitor (TPM) 
-a program that controls data transfer between clients and servers in 
order to provide a consistent environment for Online Transaction 
Processing) can be used to reduce the number of connections to the 
database server. 
ü It maps quite naturally to the Web environment, with a Web browser 
acting as the "thin" client, and a Web server acting as the application 
server.
10 
Functions of a DBMS 
A good DBMS should furnish a number of capabilities. The list of 
features that a DBMS should furnish includes the following: 
1. Data storage, retrieval and update: the ability to store, retrieve, and 
update the data that is in the database - the fundamental function of a 
DBMS. Unless a DBMS provides this facility, further discussion of 
what a DBMS can do is irrelevant. In storing, updating, and retrieving 
data, it should not be incumbent upon the user to be aware of the 
system's internal structures or the procedures used to manipulate these 
structures. This manipulation is strictly the responsibility of the DBMS 
2. Meta-data storage, retrieval and update: A user-accessible catalog 
in which descriptions of data items are stored and which is accessible 
to users. A key feature of a DBMS is the provision of an integrated 
system catalog to hold data about the structure of the database, users, 
applications, and so on. The catalog is expected to be accessible to 
users as well as to the DBMS. Typically, the system catalog stores: 
- names, types and sizes of data items, 
- integrity constraints on the data, 
- names of authorized users who have access to data. 
3. Transaction support. A transaction can be defined as being an action, 
or series of actions, carried out by a single user or application 
program, which access or changes the contents of the database. For 
example, a simple transaction will be to add a new customer in the 
database, to update the price of one product or a more complex one to 
delete a sale agent and to reassign his customers to others sales agents. 
If the transaction fails during execution, the database should be in 
inconsistent state: some changes will have been made and others not. 
To overcame this, a DBMS should provide a mechanism that will 
ensure either that all the updates corresponding to a given transaction 
are made or that none of them are made. 
We can use the famous "ACID test" when deciding whether or not a 
database management system is adequate for handling transactions. An 
adequate system has the following properties:
ü Atomicity: results of a transaction's execution are either all committed 
11 
or all rolled back. All changes take effect, or none do. . 
ü Consistency: the database is transformed from one valid state to 
another valid state. This defines a transaction as legal only if it obeys 
user-defined integrity constraints. Illegal transactions aren't allowed 
and, if an integrity constraint can't be satisfied then the transaction is 
rolled back. 
ü Isolation: the results of a transaction are invisible to other transactions 
until the transaction is complete. 
ü Durability: once committed (completed), the results of a transaction 
are permanent and survive future system and media failures. 
4. Concurrency control services (support for shared update): a 
mechanism to ensure accuracy when several users are updating the 
database at the same time. Concurrent access is relatively easy if all 
users are only reading data, as there is no way they can interfere with 
one another. When two or more users are accessing the database 
simultaneously and at least one of them is updating data, there may be 
interference that can result in inconsistencies. One approach that 
ensures correct results is locking; as long as a portion of the database is 
locked by one user, other users cannot gain access to it. 
5. Recovery services: a mechanism for recovering the database in the 
event that the database is damaged in any way. This may be the 
result of a system crash, media failure, a hardware or software error 
causing the DBMS to stop, or it may be the result of the user detecting 
an error during the transaction and aborting the transaction before it 
completes. In all the cases, the DBMS must provide a mechanism to 
recover the database to a consistent state. The simplest approach to 
recovery involves periodically making a copy of the database (called a 
backup or a save). If a problem occurs, the database is recovered by 
copying this backup copy over it. In effect, the damage is undone by 
returning the database to the state it was in when the last backup was 
made. 
6. Security services: a mechanism to ensure that only authorized users 
can access the database. A DBMS must furnish a mechanism that 
restricts access to the database to authorized users. The term security
refers to the protection of the database against unauthorized (or even 
illegal) access, either intentional or accidental. 
7. Integrity services: mechanisms to ensure that certain rules are 
followed with regard to data in the database and any changes that are 
made in the data. Data integrity refers to the correctness and 
consistency of stored data. It can be considered as another type of 
database protection. While it's related to security, it has wider 
implications; integrity is concerned with the quality of data itself. 
Integrity is usually expressed in terms of constraints, which are 
consistency rules that the database is not permitted to violate. The 
types of constraints that may be present fall into the following four 
categories: 
§ Data type. The data entered for any column should be consistent with 
the data type for that column. For a numeric column, only numbers 
should be allowed to be entered. If the column is a date, only a 
legitimate date (in the form MMDDYY or MM/DD/YY) should be 
permitted. 
§ Legal values. It may be that for certain columns, not every possible 
value that is of the right type is legitimate. For example, even though 
CREDLIM is a numeric column, only the values 400, 500, 700, 800, 
and 1,000 may be valid. 
§ Format. It may be that certain columns have a very special format that 
12 
must be followed. 
§ Key constraints. There are two types of key constraints: primary key 
constraints and foreign key constraints. Primary key constraints 
enforce the uniqueness of the primary key. For example, forbidding 
the addition of a customer whose number matched the number of a 
customer already in the database would be a primary key constraint. 
Foreign key constraints enforce the fact that a value for a foreign key 
must match the value of the primary key for some row in another table. 
Forbidding the addition of a customer whose sales agent was not 
already in the database would be an example of a foreign key 
constraint. 
An integrity constraint can be treated in one of four ways: 
a) The constraint can be ignored, in which case no attempt is made to 
enforce the constraint. 
b) The burden of enforcing the constraint can be placed on the users of 
the system. This means that users must be careful that any changes 
they make in the database do not violate the constraint.
c) The burden can be placed on programmers. Logic to enforce the 
constraint is then built into programs. Users must update the database 
only by means of these programs and not through any of the built-in 
entry facilities provided by the DBMS, since these would allow 
violation of the constraint. The programs are designed to reject any 
attempt on the part of the user to update the database in such a way 
that the constraint is violated. 
d) The burden can be placed on the DBMS. The constraint is specified to 
the DBMS, which then rejects any attempt to update the database in 
such a way that the constraint is violated. 
The best approach is the last one. Unfortunately, most DBMS don't 
have all the necessary capabilities to enforce the various types of integrity. 
Usually, the approach that is taken is a combination of the (c) and (d) in 
the foregoing list. We let the DBMS enforce any of the constraints that it 
is capable of enforcing; application programs enforce other constraints. 
We might also create a special program whose sole purpose would be to 
examine the data in the database to determine whether any constraints had 
been violated; this program would be run periodically. Corrective action 
could be taken to remedy any violations that were discovered by leans of 
this program. 
8. Support for data communication. Most users access the database 
from terminals. Sometimes, these terminals are connected directly to 
the computer hosting the DBMS. In other cases, the terminals are at 
remote locations and communicate with the computer hosting the 
DBMS over a network. In either case, the DBMS must be capable of 
integrating with networking/communication software, 
9. Services to promote data independence: facilities to support the 
independence of programs from the structure of the database. One of 
the advantages of working with a DBMS is data independence; that is, 
the property that changes can be made in the layout of a database 
without application programs necessarily being affected. Data 
independence is normally achieved through a view mechanism; there 
are usually several types of changes that can be made to the physical 
characteristics of the database without affecting the views, such as 
using different file organizations or modifying indexes - this is called 
physical data independence. However, complete logical data 
independence is more difficult to achieve; the addition of a new file or 
13
field can usually be accommodated, but not their removal (in some 
systems, any type of change to a file structure is prohibited). 
10. Utility services: DBMS-provided services that assist in the general 
maintenance of the database. Utility programs help the Database 
Administrator to manage the database effectively. Following is a list of 
such services that may be provided by a DBMS. 
• Services that permit changes to be made in the database structure 
(adding new tables or columns, deleting existing tables or columns, 
changing the name or characteristics of a column, and so on). 
• Services that permit the addition of new indexes and the deletion of 
14 
indexes that are no longer wanted. 
• Import and export facilities from other software products. For 
example, these services allow data to be transferred in a relatively easy 
fashion between the DBMS and a spreadsheet, word processing, or 
graphics program, or to load and unload data from or to flat files. 
• Monitoring facilities, to monitor database usage and operation. 
• Several of the services that form a part of the fourth-generation 
environment are also furnished by some of the better DBMS. These 
include such things as easy-to-use edit and query capabilities, screen 
generators, report generators, and so on. 
• Access to both procedural and nonprocedural languages. 
• An easy-to-use graphical user interface that allows users to tap the 
power of the DBMS without having to resort to a complicated set of 
commands. 
The actual level of functionality offered by a DBMS differs from 
product to product. For example, a DBMS for a PC may not support 
concurrent shared access, and it may only provide limited security, 
integrity and recovery control. Modern, large multi-user DBMS products 
offer all the above functions and much more. 
DATABASE ADMINISTRATION AND SECURITY 
Data administration and database administration 
The Data Administrator (DA) and Database Administrator (DBA) 
are responsible for managing and controlling the activities associated with 
the corporate data and the corporate database, respectively. Depending on
the size and complexity of the organization and database system, the DA 
and DBA can be the responsibility of one or more people. 
Data administration - the management and control of the 
corporate data, including database planning, development and 
maintenance of standards, policies and procedures, and logical database 
design. The DA is responsible for the corporate data, which includes non-computerized 
data, and in practice is often concerned with managing the 
shared data of users or business application areas of an organization. He 
must ensure that the application of database technologies supports the 
corporate objectives. 
Database administration - the management and control of the 
corporate database system, including physical database design and 
implementation, setting security and integrity controls, monitoring system 
performance, and reorganizing the database as necessary. The DBA is 
more technically oriented than the DA, requiring knowledge of specific 
DBMSs and the operating system environment. The primary 
responsibilities of the DBA are centered on developing and maintaining 
systems using the DBMS software to its full extent. 
In some organizations, data administration is a distinct business 
15 
area, in others it may be combined with database administration. 
Data administration Database administration 
Involved in strategic IS planning Evaluates new DBMSs 
Determines long-term goals Executes plans to achieve goals 
Determines standards, policies and 
procedures 
Enforces standards, policies and 
procedures 
Determined data requirements Implements data requirements 
Develops logical database design Develops physical database design 
Develops and maintains corporate data 
model 
Implements physical database design 
Coordinates database development Monitors and controls database use 
Managerial orientation Technical orientation 
DBMS independent DBMS dependent 
Database security 
Database security is the mechanism that protect the database against 
intentional or accidental threats. Database security encompasses hardware, 
software, people and data. This need for security is due to the increasing 
amounts of crucial corporate data being stored on computer and the
acceptance that any loss or unavailability of this data could be potentially 
disastrous. 
A database represents nowadays an essential corporate resource that 
should be properly secured using appropriate controls. Database security is 
considered in relation to the following outcomes: 
- theft and fraud, 
- loss of confidentiality (secrecy), 
- loss of privacy, 
- loss of integrity, 
- loss of availability. 
An organization needs to identify the types of threats it may be subjected 
to (we understand by threats any situations or events, whether intentional 
or unintentional, that may adversely affect a system and consequently the 
organization) and initiate appropriate plans and countermeasures, 
considering also the costs of implementing them. 
The types of countermeasures to threats on database systems range from 
physical controls to administrative procedures. Despite the range of 
computer-based controls that are available, generally, the security of a 
DBMS is only as good as that of the operating system, owing to their close 
association. The most widely used computer-based security controls for a 
multi-user environment are: 
1) Authorization (access control) - the granting of a right or privilege 
that enables a subject to have legitimate access to a database 
system or a database system's object. The process of authorization 
involves authentication (a mechanism that determines whether a user 
is who he or she claims to be) of a subject (a user) requesting access to 
an object (a database table, view, procedure or any other object that 
can be created within the database system). A system administrator is 
usually responsible for permitting user's access, by creating individual 
users accounts and passwords. Once a user is given permission to use a 
DBMS, various other privileges may also be automatically associated 
with it. Privileges are granted to users to accomplish the tasks required 
for their jobs. 
2) Views - virtual tables that does not necessarily exist in the database 
but can be produced upon request by a particular user, at the time 
of request. The view mechanism provides a powerful and flexible 
security mechanism by hiding parts of the database from certain users. 
16
3) Backup and recovery - the process of periodically taking a copy of 
the database and log file (and possibly programs) onto offline 
storage media in order to assist the recovery of the database 
following failure. 
4) To keep track of database transactions, the DBMS maintains a special 
file called a log file (or journal) that contains information about all 
updates to the database. A DBMS should provide logging facilities, 
sometimes referred to as journaling, which keep track of the current 
state of transactions and database changes, to provide support for 
recovery procedures. 
5) Integrity -integrity constraints contribute to maintaining a secure 
database system by preventing data from becoming invalid, and hence 
giving misleading or incorrect results. 
6) Encryption - the encoding of the data by a special algorithm that 
renders the data unreadable by any program without the 
decryption key. 
7) Redundant Array of Independent Disks (RAID) - the hardware that 
DBMS is running on must be fault-tolerant, meaning that the DBMS 
should continue to operate even if one of the hardware components 
fails. RAID technology works by having a large disk array comprising 
an arrangement of several independent disks that are organized to 
improve reliability and at the same time to increase performance. 
17 
DATABASE APPROACH - ADVANTAGES AND 
DISADVANTAGES 
The main benefits of the database approach are: 
1. Control of data redundancy 
The database approach eliminates redundancy where possible; 
previously separate (and redundant) data files are integrated into a single, 
logical structure. In addition, each data item occurrence is ideally recorded 
in only one place in the database. That doesn’t mean that all redundancy 
can or should be eliminated. Sometimes there are valid reasons for storing
multiple copies of the same data. However, the amount of redundancy 
inherent in the database is controlled. 
18 
2. Data consistency 
By controlling (or eliminating) data redundancy, we greatly reduce the 
risk of inconsistencies occurring. If data is stored only once in the 
database, any update to it's value has to be performed only once and the 
new value is immediately available to all users. When controlled 
redundancy is permitted in the database, the database system itself should 
enforce consistency by updating each occurrence of a data item when a 
change occurs – that means that the DBMS could guarantee that the 
database is never inconsistent as seen by the user, by ensuring that any 
change made to either of the two entities is automatically applied to the 
other one also (process known as “propagating updates”). However, few 
commercially available systems today are capable of automatically 
propagating updates in this manner; most current products do not support 
controlled redundancy at all, except in certain special situations. 
3. Sharing of data 
In a file-based approach, typically files are owned by the people or 
departments that use them. On the other hand, the database belongs to the 
entire organization and can be shared by all authorized users. Sharing 
means not only that existing applications can share the data in the 
database, but also that new applications can be developed to operate 
against that same stored data. In other words, it might be possible to 
satisfy the data requirements of new applications without having to create 
any additional stored data. The new applications can also rely on the 
functions provided by the DBMS, such as data definition and 
manipulation, concurrency and recovery control, rather than having to 
provide these functions themselves. 
4. Improved data integrity 
The problem of integrity is the problem of ensuring that the data in the 
database is accurate. Database integrity is usually expressed in terms of 
constraints, which are consistency rules that the database is not permitted 
to violate. Inconsistency between two entries that purport to represent the 
same “fact” is an example of lack of integrity; that particular problem can 
arise only if redundancy exists in the stored data. Even if there is no 
redundancy, however, the database might still contain incorrect 
information.
Centralized control of the database can help in avoiding such problems 
– insofar as they can be avoided – by permitting the data administrator to 
define (and the DBA to implement) integrity rules to be checked whenever 
any data update operation is attempted. 
It is worth pointing out that data integrity is even more important in a 
multi-user database than it is in a “private files” environment, precisely 
because the database is shared. For without appropriate controls it would 
be possible for one user to update the database incorrectly, thereby 
generating bad data and so “infecting” other innocent users of that data. 
19 
5. Standards can be enforced 
Establishing the data administration function is an important part of 
the database approach. This organizational function has authority for 
defining and enforcing data standards. With central control of the 
database, data base administrator can ensure that all applicable standards 
are observed in the representation of the data. Applicable standards might 
include any or all of the following: corporate, installation, departmental, 
industry, national and international standards. Standardizing data 
representation is particularly desirable as an aid to data interchange, or 
migration of data between systems. Likewise, data naming and 
documentation standards are also very desirable as an aid to data sharing 
and understandability. 
6. Improved security 
The data administration function has complete jurisdiction over the 
database and is responsible for establishing controls for accessing, 
updating and protecting data. The DBA can ensure that the only means of 
access to the database is through the proper channels, and hence can 
define security rules to be checked whenever access is attempted to 
sensitive data. Different rules can be established for each type of access to 
each piece of information in the database. 
Without such rules the security of data might actually be more at risk than 
in a traditional (dispersed) filing system; centralized nature of a database 
system in a sense requires that a good security system be in place also. 
7. Conflicting requirements can be balanced 
Knowing the overall requirements of the organization – as opposed to 
the requirements of individual users – the DBA can so structure the system 
as to provide an overall service that is “best for the organization”. For 
example, a representation can be chosen for the data in storage that gives
fast access for the most important applications (possibly at the cost of 
poorer performance for certain other applications). 
20 
8. Increased productivity 
A major advantage of the database approach is that the cost and time 
for developing new business applications are greatly reduced. Once the 
database has been designed and implemented, a programmer can code and 
debug a new application at least two to four times faster than with 
conventional data files; the reason for this improvement is that the 
programmer is no longer saddled with the burden of designing, building 
and maintaining master files. 
9. The provision of data independence 
Applications implemented on older systems tend to be data-depended. 
What this means is that the way in which the data is organized in 
secondary storage, and the technique for accessing it, are both dictated by 
the requirements of the application under consideration, and moreover that 
knowledge of that data organization and that access technique is built into 
the application logic and code. It is impossible to change the storage 
structure (how the data is physically stored) or access technique (how it is 
accessed) without affecting the application, probably drastically. 
In a database system, however, it would be extremely undesirable to 
allow applications to be data-dependent, for at least the following two 
reasons: 
• Different applications will need different views of the same data 
• The DBA must have the freedom to change the storage structure or 
access technique in response to changing requirements, without having 
to modify existing applications. For example, new kinds of data might 
be added to the database; new standards might be adopted; application 
priorities might change; new types of storage device might become 
available; and so on. If applications are data-depended, such changes 
will typically require corresponding changes to be made to programs, 
thus typing out programmer effort that would otherwise be available 
for the creation of new applications. 
It follows that the provision of data independence is a major 
objective of database systems. Data independence can be defined as the 
immunity of applications to change in storage structure and access 
technique. The database should be able to grow without affecting existing 
applications; that is probably the single most important reason for 
requiring data independence in the first place.
However, data independence is not an absolute – different systems 
provide it in different degrees; in fact, few systems, if any, provide no data 
independence at all – it is just that some systems are less data-dependent 
than others. 
There are, however, some disadvantages of the database approach, 
such as: 
1. Complexity. A DBMS is an extremely complex piece of software, and 
all users (database designers and developers, database administrators 
and end-users) must understand the DBMS functionality to take full 
advantage of it. 
2. Cost of DBMS. The cost of DBMS varies significantly, depending on 
the environment and functionality provided. There is also the recurrent 
annual maintenance cost, which is a percentage of the list price. 
3. Cost of conversion. In some situations, the cost of the DBMS and 
extra hardware may be insignificant compared with the cost of 
converting existing applications to run on the new DBMS and 
hardware. This cost is one of the main reasons why some companies 
feel tied with their current systems and cannot switch to more modern 
database technology. 
4. Performance. Typically, a file-based system is written for a specific 
application, such as invoicing. As a result, performance is generally 
very good. A DBMS is written to be more general, to cater for many 
applications rather that just one. The effect is that some applications 
may not run as fast using a DBMS as they did before. 
5. Higher impact of a failure. The centralization of resources increases 
the vulnerability of the system. Since all users and applications rely on 
the availability of the DBMS, the failure of any component can bring 
operations to a complete halt until the failure is repaired. 
21

More Related Content

What's hot

Data base management system
Data base management systemData base management system
Data base management system
Bibek Regmi
 
Database system-DBMS
Database system-DBMSDatabase system-DBMS
Database system-DBMS
ikjsamuel
 
Importance of database design (1)
Importance of database design (1)Importance of database design (1)
Importance of database design (1)
yhen06
 
Database Management System
Database Management SystemDatabase Management System
Database Management System
Tamur Iqbal
 
Data base management system
Data base management systemData base management system
Data base management system
Navneet Jingar
 
Database system environment ppt.
Database system environment ppt.Database system environment ppt.
Database system environment ppt.
yhen06
 
Mis assignment (database)
Mis assignment (database)Mis assignment (database)
Mis assignment (database)
Muhammad Sultan Bhatti
 
Database Presentation
Database PresentationDatabase Presentation
Database Presentation
a9oolq8
 
DATABASE Fp304 chapter 1
DATABASE Fp304   chapter 1DATABASE Fp304   chapter 1
DATABASE Fp304 chapter 1
Radio Deejay
 
Database Design and Implementation
Database Design and ImplementationDatabase Design and Implementation
Database Design and Implementation
Christian Reina
 
Uses of dbms
Uses of dbmsUses of dbms
Uses of dbms
MISY
 
File systems versus a dbms
File systems versus a dbmsFile systems versus a dbms
File systems versus a dbms
RituBhargava7
 
Continuation prelims database system environment
Continuation prelims   database system environmentContinuation prelims   database system environment
Continuation prelims database system environment
Jeph Pedrigal
 
Database management system
Database management systemDatabase management system
Database management system
Simran Kaur
 
Chapter2
Chapter2Chapter2
Chapter2
Jafar Nesargi
 
Dbms ppt
Dbms pptDbms ppt
Dbms ppt
Chinnu Shimna
 
Database Management System ppt
Database Management System pptDatabase Management System ppt
Database Management System ppt
OECLIB Odisha Electronics Control Library
 
Assign 1
Assign 1Assign 1
Assign 1
guestffcfdd
 
Chapter 1 Fundamentals of Database Management System
Chapter 1 Fundamentals of Database Management SystemChapter 1 Fundamentals of Database Management System
Chapter 1 Fundamentals of Database Management System
Eddyzulham Mahluzydde
 
ch1
ch1ch1

What's hot (20)

Data base management system
Data base management systemData base management system
Data base management system
 
Database system-DBMS
Database system-DBMSDatabase system-DBMS
Database system-DBMS
 
Importance of database design (1)
Importance of database design (1)Importance of database design (1)
Importance of database design (1)
 
Database Management System
Database Management SystemDatabase Management System
Database Management System
 
Data base management system
Data base management systemData base management system
Data base management system
 
Database system environment ppt.
Database system environment ppt.Database system environment ppt.
Database system environment ppt.
 
Mis assignment (database)
Mis assignment (database)Mis assignment (database)
Mis assignment (database)
 
Database Presentation
Database PresentationDatabase Presentation
Database Presentation
 
DATABASE Fp304 chapter 1
DATABASE Fp304   chapter 1DATABASE Fp304   chapter 1
DATABASE Fp304 chapter 1
 
Database Design and Implementation
Database Design and ImplementationDatabase Design and Implementation
Database Design and Implementation
 
Uses of dbms
Uses of dbmsUses of dbms
Uses of dbms
 
File systems versus a dbms
File systems versus a dbmsFile systems versus a dbms
File systems versus a dbms
 
Continuation prelims database system environment
Continuation prelims   database system environmentContinuation prelims   database system environment
Continuation prelims database system environment
 
Database management system
Database management systemDatabase management system
Database management system
 
Chapter2
Chapter2Chapter2
Chapter2
 
Dbms ppt
Dbms pptDbms ppt
Dbms ppt
 
Database Management System ppt
Database Management System pptDatabase Management System ppt
Database Management System ppt
 
Assign 1
Assign 1Assign 1
Assign 1
 
Chapter 1 Fundamentals of Database Management System
Chapter 1 Fundamentals of Database Management SystemChapter 1 Fundamentals of Database Management System
Chapter 1 Fundamentals of Database Management System
 
ch1
ch1ch1
ch1
 

Viewers also liked

Sql ch 9 - data integrity
Sql ch 9 - data integritySql ch 9 - data integrity
Sql ch 9 - data integrity
Mukesh Tekwani
 
integrity constraints
integrity constraintsintegrity constraints
integrity constraints
madhav bansal
 
Integrity Constraints
Integrity ConstraintsIntegrity Constraints
Integrity Constraints
madhav bansal
 
Slide 6 er strong & weak entity
Slide 6 er  strong & weak entitySlide 6 er  strong & weak entity
Slide 6 er strong & weak entity
Visakh V
 
Database Relationships
Database RelationshipsDatabase Relationships
Database Relationships
wmassie
 
File system-and-database-chapter01-connoly
File system-and-database-chapter01-connolyFile system-and-database-chapter01-connoly
File system-and-database-chapter01-connoly
Temma Tems
 
Data integrity Dbms presentation 12 cs 18
Data integrity Dbms presentation 12 cs 18Data integrity Dbms presentation 12 cs 18
Data integrity Dbms presentation 12 cs 18
Engr Imran Ashraf
 
Data integrity
Data integrityData integrity
Data integrity
Kiran Kota
 
Files Vs DataBase
Files Vs DataBaseFiles Vs DataBase
Files Vs DataBase
Dr. C.V. Suresh Babu
 
All data models in dbms
All data models in dbmsAll data models in dbms
All data models in dbms
Naresh Kumar
 
IP adress and routing(networking)
IP adress and routing(networking)IP adress and routing(networking)
IP adress and routing(networking)
welcometofacebook
 
Database Management System Introduction
Database Management System IntroductionDatabase Management System Introduction
Database Management System Introduction
Smriti Jain
 
DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...
DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...
DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...
Beat Signer
 
Dbms models
Dbms modelsDbms models
Dbms models
devgocool
 
Data Modeling PPT
Data Modeling PPTData Modeling PPT
Data Modeling PPT
Trinath
 
Database Management Systems (DBMS)
Database Management Systems (DBMS)Database Management Systems (DBMS)
Database Management Systems (DBMS)
Dimara Hakim
 
Data Base Management System
Data Base Management SystemData Base Management System
Data Base Management System
Dr. C.V. Suresh Babu
 
Switching Techniques
Switching TechniquesSwitching Techniques
Switching Techniques
tameemyousaf
 
Database Design Slide 1
Database Design Slide 1Database Design Slide 1
Database Design Slide 1
ahfiki
 
Basic DBMS ppt
Basic DBMS pptBasic DBMS ppt
Basic DBMS ppt
dangwalrajendra888
 

Viewers also liked (20)

Sql ch 9 - data integrity
Sql ch 9 - data integritySql ch 9 - data integrity
Sql ch 9 - data integrity
 
integrity constraints
integrity constraintsintegrity constraints
integrity constraints
 
Integrity Constraints
Integrity ConstraintsIntegrity Constraints
Integrity Constraints
 
Slide 6 er strong & weak entity
Slide 6 er  strong & weak entitySlide 6 er  strong & weak entity
Slide 6 er strong & weak entity
 
Database Relationships
Database RelationshipsDatabase Relationships
Database Relationships
 
File system-and-database-chapter01-connoly
File system-and-database-chapter01-connolyFile system-and-database-chapter01-connoly
File system-and-database-chapter01-connoly
 
Data integrity Dbms presentation 12 cs 18
Data integrity Dbms presentation 12 cs 18Data integrity Dbms presentation 12 cs 18
Data integrity Dbms presentation 12 cs 18
 
Data integrity
Data integrityData integrity
Data integrity
 
Files Vs DataBase
Files Vs DataBaseFiles Vs DataBase
Files Vs DataBase
 
All data models in dbms
All data models in dbmsAll data models in dbms
All data models in dbms
 
IP adress and routing(networking)
IP adress and routing(networking)IP adress and routing(networking)
IP adress and routing(networking)
 
Database Management System Introduction
Database Management System IntroductionDatabase Management System Introduction
Database Management System Introduction
 
DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...
DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...
DBMS Architectures and Features - Lecture 7 - Introduction to Databases (1007...
 
Dbms models
Dbms modelsDbms models
Dbms models
 
Data Modeling PPT
Data Modeling PPTData Modeling PPT
Data Modeling PPT
 
Database Management Systems (DBMS)
Database Management Systems (DBMS)Database Management Systems (DBMS)
Database Management Systems (DBMS)
 
Data Base Management System
Data Base Management SystemData Base Management System
Data Base Management System
 
Switching Techniques
Switching TechniquesSwitching Techniques
Switching Techniques
 
Database Design Slide 1
Database Design Slide 1Database Design Slide 1
Database Design Slide 1
 
Basic DBMS ppt
Basic DBMS pptBasic DBMS ppt
Basic DBMS ppt
 

Similar to Database & dbms

database ppt(2)
database ppt(2)database ppt(2)
database ppt(2)
EshetuGeletu2
 
1. Chapter One.pdf
1. Chapter One.pdf1. Chapter One.pdf
1. Chapter One.pdf
fikadumola
 
DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1
DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1
DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1
Raj vardhan
 
Database System Concepts
Database System ConceptsDatabase System Concepts
Database System Concepts
Ranilesh Raveendran
 
Complete dbms notes
Complete dbms notesComplete dbms notes
Complete dbms notes
Tanya Makkar
 
Data Base Management Systems
Data Base Management SystemsData Base Management Systems
Data Base Management Systems
Raj vardhan
 
DBMS-INTRODUCTION.pptx
DBMS-INTRODUCTION.pptxDBMS-INTRODUCTION.pptx
DBMS-INTRODUCTION.pptx
DivyaKS12
 
chapter 1-Introduction Fundamentals of database system.pdf
chapter 1-Introduction Fundamentals of database system.pdfchapter 1-Introduction Fundamentals of database system.pdf
chapter 1-Introduction Fundamentals of database system.pdf
MisganawAbeje1
 
Chap1-Introduction to database systems.ppt
Chap1-Introduction to database systems.pptChap1-Introduction to database systems.ppt
Chap1-Introduction to database systems.ppt
LisaMalar
 
Data base management system
Data base management systemData base management system
Data base management system
Suneel Dogra
 
Chapter one
Chapter oneChapter one
Chapter one
Dawod Yimer
 
DBMS NOTES UNIT I FINAL.docx was prasented
DBMS NOTES UNIT I FINAL.docx was prasentedDBMS NOTES UNIT I FINAL.docx was prasented
DBMS NOTES UNIT I FINAL.docx was prasented
rajitha ellandula
 
DBMS NOTES UNIT I FINAL.docx used for preparation
DBMS NOTES UNIT I FINAL.docx used for preparationDBMS NOTES UNIT I FINAL.docx used for preparation
DBMS NOTES UNIT I FINAL.docx used for preparation
rajitha ellandula
 
Unit 2 rdbms study_material
Unit 2  rdbms study_materialUnit 2  rdbms study_material
Unit 2 rdbms study_material
gayaramesh
 
Ch01
Ch01Ch01
Introduction & history of dbms
Introduction & history of dbmsIntroduction & history of dbms
Introduction & history of dbms
sethu pm
 
Mis chapter 7 database systems
Mis chapter 7 database systemsMis chapter 7 database systems
Mis chapter 7 database systems
Filmon Habtemichael Tesfai
 
En ch01
En ch01En ch01
En ch01
anibapi
 
ms-11.pdf
ms-11.pdfms-11.pdf
ms-11.pdf
NikitaKumari71
 
Database Management System ( Dbms )
Database Management System ( Dbms )Database Management System ( Dbms )
Database Management System ( Dbms )
Kimberly Brooks
 

Similar to Database & dbms (20)

database ppt(2)
database ppt(2)database ppt(2)
database ppt(2)
 
1. Chapter One.pdf
1. Chapter One.pdf1. Chapter One.pdf
1. Chapter One.pdf
 
DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1
DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1
DATABASE MANAGEMENT SYSTEM UNIT-I Chapter-1
 
Database System Concepts
Database System ConceptsDatabase System Concepts
Database System Concepts
 
Complete dbms notes
Complete dbms notesComplete dbms notes
Complete dbms notes
 
Data Base Management Systems
Data Base Management SystemsData Base Management Systems
Data Base Management Systems
 
DBMS-INTRODUCTION.pptx
DBMS-INTRODUCTION.pptxDBMS-INTRODUCTION.pptx
DBMS-INTRODUCTION.pptx
 
chapter 1-Introduction Fundamentals of database system.pdf
chapter 1-Introduction Fundamentals of database system.pdfchapter 1-Introduction Fundamentals of database system.pdf
chapter 1-Introduction Fundamentals of database system.pdf
 
Chap1-Introduction to database systems.ppt
Chap1-Introduction to database systems.pptChap1-Introduction to database systems.ppt
Chap1-Introduction to database systems.ppt
 
Data base management system
Data base management systemData base management system
Data base management system
 
Chapter one
Chapter oneChapter one
Chapter one
 
DBMS NOTES UNIT I FINAL.docx was prasented
DBMS NOTES UNIT I FINAL.docx was prasentedDBMS NOTES UNIT I FINAL.docx was prasented
DBMS NOTES UNIT I FINAL.docx was prasented
 
DBMS NOTES UNIT I FINAL.docx used for preparation
DBMS NOTES UNIT I FINAL.docx used for preparationDBMS NOTES UNIT I FINAL.docx used for preparation
DBMS NOTES UNIT I FINAL.docx used for preparation
 
Unit 2 rdbms study_material
Unit 2  rdbms study_materialUnit 2  rdbms study_material
Unit 2 rdbms study_material
 
Ch01
Ch01Ch01
Ch01
 
Introduction & history of dbms
Introduction & history of dbmsIntroduction & history of dbms
Introduction & history of dbms
 
Mis chapter 7 database systems
Mis chapter 7 database systemsMis chapter 7 database systems
Mis chapter 7 database systems
 
En ch01
En ch01En ch01
En ch01
 
ms-11.pdf
ms-11.pdfms-11.pdf
ms-11.pdf
 
Database Management System ( Dbms )
Database Management System ( Dbms )Database Management System ( Dbms )
Database Management System ( Dbms )
 

More from Diana Diana

Finance 02?
Finance 02?Finance 02?
Finance 02?
Diana Diana
 
Bei 13
Bei 13Bei 13
Bei 13
Diana Diana
 
Bei 11
Bei 11Bei 11
Bei 11
Diana Diana
 
Bei 07
Bei 07Bei 07
Bei 07
Diana Diana
 
Bei 06
Bei 06Bei 06
Bei 06
Diana Diana
 
Bei 04
Bei 04Bei 04
Bei 04
Diana Diana
 
Bei 14
Bei 14Bei 14
Bei 14
Diana Diana
 
Bei 10
Bei 10Bei 10
Bei 10
Diana Diana
 
Bei 02
Bei 02Bei 02
Bei 02
Diana Diana
 
Bei lecture 3_types_of_companies
Bei lecture 3_types_of_companiesBei lecture 3_types_of_companies
Bei lecture 3_types_of_companies
Diana Diana
 
Bei lecture 1_introduction
Bei lecture 1_introductionBei lecture 1_introduction
Bei lecture 1_introduction
Diana Diana
 
Finance 01
Finance 01Finance 01
Finance 01
Diana Diana
 
Finance 03
Finance 03Finance 03
Finance 03
Diana Diana
 
Data models and ro
Data models and roData models and ro
Data models and ro
Diana Diana
 
Sql
SqlSql
Bm 12 leadership (ii)
Bm 12 leadership (ii)Bm 12 leadership (ii)
Bm 12 leadership (ii)
Diana Diana
 
Bm 10 organizational_intellectual capital
Bm 10 organizational_intellectual capitalBm 10 organizational_intellectual capital
Bm 10 organizational_intellectual capital
Diana Diana
 
Bm 09 organizational_culture
Bm 09 organizational_cultureBm 09 organizational_culture
Bm 09 organizational_culture
Diana Diana
 
Bm 08 organizational_knowledge and learning
Bm 08 organizational_knowledge and learningBm 08 organizational_knowledge and learning
Bm 08 organizational_knowledge and learning
Diana Diana
 
Bm 07 Organization design
Bm 07 Organization designBm 07 Organization design
Bm 07 Organization design
Diana Diana
 

More from Diana Diana (20)

Finance 02?
Finance 02?Finance 02?
Finance 02?
 
Bei 13
Bei 13Bei 13
Bei 13
 
Bei 11
Bei 11Bei 11
Bei 11
 
Bei 07
Bei 07Bei 07
Bei 07
 
Bei 06
Bei 06Bei 06
Bei 06
 
Bei 04
Bei 04Bei 04
Bei 04
 
Bei 14
Bei 14Bei 14
Bei 14
 
Bei 10
Bei 10Bei 10
Bei 10
 
Bei 02
Bei 02Bei 02
Bei 02
 
Bei lecture 3_types_of_companies
Bei lecture 3_types_of_companiesBei lecture 3_types_of_companies
Bei lecture 3_types_of_companies
 
Bei lecture 1_introduction
Bei lecture 1_introductionBei lecture 1_introduction
Bei lecture 1_introduction
 
Finance 01
Finance 01Finance 01
Finance 01
 
Finance 03
Finance 03Finance 03
Finance 03
 
Data models and ro
Data models and roData models and ro
Data models and ro
 
Sql
SqlSql
Sql
 
Bm 12 leadership (ii)
Bm 12 leadership (ii)Bm 12 leadership (ii)
Bm 12 leadership (ii)
 
Bm 10 organizational_intellectual capital
Bm 10 organizational_intellectual capitalBm 10 organizational_intellectual capital
Bm 10 organizational_intellectual capital
 
Bm 09 organizational_culture
Bm 09 organizational_cultureBm 09 organizational_culture
Bm 09 organizational_culture
 
Bm 08 organizational_knowledge and learning
Bm 08 organizational_knowledge and learningBm 08 organizational_knowledge and learning
Bm 08 organizational_knowledge and learning
 
Bm 07 Organization design
Bm 07 Organization designBm 07 Organization design
Bm 07 Organization design
 

Recently uploaded

AI at Work​ The demystification of AI and real-world stories on how to apply ...
AI at Work​ The demystification of AI and real-world stories on how to apply ...AI at Work​ The demystification of AI and real-world stories on how to apply ...
AI at Work​ The demystification of AI and real-world stories on how to apply ...
Auxis Consulting & Outsourcing
 
Movers near me in Dubai , Best Packers and Movers In Dubai
Movers near me in Dubai , Best Packers and Movers In DubaiMovers near me in Dubai , Best Packers and Movers In Dubai
Movers near me in Dubai , Best Packers and Movers In Dubai
imranmalik114455
 
TALENT ACQUISITION AND MANAGEMENT LECTURE 2
TALENT ACQUISITION AND MANAGEMENT LECTURE 2TALENT ACQUISITION AND MANAGEMENT LECTURE 2
TALENT ACQUISITION AND MANAGEMENT LECTURE 2
projectseasy
 
Corporate Governance for South African Mining Companies
Corporate Governance for South African Mining CompaniesCorporate Governance for South African Mining Companies
Corporate Governance for South African Mining Companies
James AH Campbell
 
Cracking the Customer Experience Code.pptx
Cracking the Customer Experience Code.pptxCracking the Customer Experience Code.pptx
Cracking the Customer Experience Code.pptx
Workforce Group
 
ShotOniPhone campaign by Vancy macwan.pptx
ShotOniPhone campaign by Vancy macwan.pptxShotOniPhone campaign by Vancy macwan.pptx
ShotOniPhone campaign by Vancy macwan.pptx
macwanvancy
 
Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...
Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...
Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...
Aggregage
 
Data Analytics and AI Strategy Toolkit, Playbook and Templates
Data Analytics and AI Strategy Toolkit, Playbook and TemplatesData Analytics and AI Strategy Toolkit, Playbook and Templates
Data Analytics and AI Strategy Toolkit, Playbook and Templates
Aurelien Domont, MBA
 
Path to the next normal collection McKinsey
Path to the next normal collection McKinseyPath to the next normal collection McKinsey
Path to the next normal collection McKinsey
MajIman2
 
Restaurant Chiraz Sindbad Hotel Hammamet
Restaurant Chiraz Sindbad Hotel HammametRestaurant Chiraz Sindbad Hotel Hammamet
Restaurant Chiraz Sindbad Hotel Hammamet
rihabkorbi24
 
Business Model Canvas for Successful Business
Business Model Canvas for Successful BusinessBusiness Model Canvas for Successful Business
Business Model Canvas for Successful Business
SuganthiPrakash1
 
Girls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in City
Girls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in CityGirls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in City
Girls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in City
maigasapphire
 
High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...
High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...
High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...
dimplekumaridk322
 
YouTube Automation Step-by-step Guide.pdf
YouTube Automation Step-by-step Guide.pdfYouTube Automation Step-by-step Guide.pdf
YouTube Automation Step-by-step Guide.pdf
grizzyhuncho
 
Test Bank For Principles Of Cost Accounting, 17th Edition Edward J. Vander...
Test Bank For Principles Of Cost Accounting, 	  17th Edition Edward J. Vander...Test Bank For Principles Of Cost Accounting, 	  17th Edition Edward J. Vander...
Test Bank For Principles Of Cost Accounting, 17th Edition Edward J. Vander...
kevinkariuki227
 
The-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptx
The-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptxThe-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptx
The-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptx
Jindal Global University, Sonipat Haryana 131001
 
The Power of Digital Marketing in the Modern Age.pdf
The Power of Digital Marketing in the Modern Age.pdfThe Power of Digital Marketing in the Modern Age.pdf
The Power of Digital Marketing in the Modern Age.pdf
David Thomson
 
Top Digital Marketing Strategy in 2024.pdf
Top Digital Marketing Strategy in 2024.pdfTop Digital Marketing Strategy in 2024.pdf
Top Digital Marketing Strategy in 2024.pdf
Top IT Marketing
 
21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf
21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf
21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf
emmanuelpulido003
 
You Get Me! Leveraging Communication Styles in Virtual Trainingpptx
You Get Me! Leveraging Communication Styles in Virtual TrainingpptxYou Get Me! Leveraging Communication Styles in Virtual Trainingpptx
You Get Me! Leveraging Communication Styles in Virtual Trainingpptx
Cynthia Clay
 

Recently uploaded (20)

AI at Work​ The demystification of AI and real-world stories on how to apply ...
AI at Work​ The demystification of AI and real-world stories on how to apply ...AI at Work​ The demystification of AI and real-world stories on how to apply ...
AI at Work​ The demystification of AI and real-world stories on how to apply ...
 
Movers near me in Dubai , Best Packers and Movers In Dubai
Movers near me in Dubai , Best Packers and Movers In DubaiMovers near me in Dubai , Best Packers and Movers In Dubai
Movers near me in Dubai , Best Packers and Movers In Dubai
 
TALENT ACQUISITION AND MANAGEMENT LECTURE 2
TALENT ACQUISITION AND MANAGEMENT LECTURE 2TALENT ACQUISITION AND MANAGEMENT LECTURE 2
TALENT ACQUISITION AND MANAGEMENT LECTURE 2
 
Corporate Governance for South African Mining Companies
Corporate Governance for South African Mining CompaniesCorporate Governance for South African Mining Companies
Corporate Governance for South African Mining Companies
 
Cracking the Customer Experience Code.pptx
Cracking the Customer Experience Code.pptxCracking the Customer Experience Code.pptx
Cracking the Customer Experience Code.pptx
 
ShotOniPhone campaign by Vancy macwan.pptx
ShotOniPhone campaign by Vancy macwan.pptxShotOniPhone campaign by Vancy macwan.pptx
ShotOniPhone campaign by Vancy macwan.pptx
 
Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...
Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...
Don’t Get Left Behind: Leveraging Modern Product Management Across the Organi...
 
Data Analytics and AI Strategy Toolkit, Playbook and Templates
Data Analytics and AI Strategy Toolkit, Playbook and TemplatesData Analytics and AI Strategy Toolkit, Playbook and Templates
Data Analytics and AI Strategy Toolkit, Playbook and Templates
 
Path to the next normal collection McKinsey
Path to the next normal collection McKinseyPath to the next normal collection McKinsey
Path to the next normal collection McKinsey
 
Restaurant Chiraz Sindbad Hotel Hammamet
Restaurant Chiraz Sindbad Hotel HammametRestaurant Chiraz Sindbad Hotel Hammamet
Restaurant Chiraz Sindbad Hotel Hammamet
 
Business Model Canvas for Successful Business
Business Model Canvas for Successful BusinessBusiness Model Canvas for Successful Business
Business Model Canvas for Successful Business
 
Girls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in City
Girls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in CityGirls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in City
Girls Call Kharghar 9910780858 Provide Best And Top Girl Service And No1 in City
 
High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...
High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...
High Profile Girls Call Bhubaneswar 🎈🔥000XX00000 🔥💋🎈 Provide Best And Top Gir...
 
YouTube Automation Step-by-step Guide.pdf
YouTube Automation Step-by-step Guide.pdfYouTube Automation Step-by-step Guide.pdf
YouTube Automation Step-by-step Guide.pdf
 
Test Bank For Principles Of Cost Accounting, 17th Edition Edward J. Vander...
Test Bank For Principles Of Cost Accounting, 	  17th Edition Edward J. Vander...Test Bank For Principles Of Cost Accounting, 	  17th Edition Edward J. Vander...
Test Bank For Principles Of Cost Accounting, 17th Edition Edward J. Vander...
 
The-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptx
The-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptxThe-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptx
The-Three-Pillars-of-Doctoral-Research-What-Why-and-How (1).pptx
 
The Power of Digital Marketing in the Modern Age.pdf
The Power of Digital Marketing in the Modern Age.pdfThe Power of Digital Marketing in the Modern Age.pdf
The Power of Digital Marketing in the Modern Age.pdf
 
Top Digital Marketing Strategy in 2024.pdf
Top Digital Marketing Strategy in 2024.pdfTop Digital Marketing Strategy in 2024.pdf
Top Digital Marketing Strategy in 2024.pdf
 
21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf
21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf
21stcenturyskillsframeworkfinalpresentation2-240509214747-71edb7ee.pdf
 
You Get Me! Leveraging Communication Styles in Virtual Trainingpptx
You Get Me! Leveraging Communication Styles in Virtual TrainingpptxYou Get Me! Leveraging Communication Styles in Virtual Trainingpptx
You Get Me! Leveraging Communication Styles in Virtual Trainingpptx
 

Database & dbms

  • 1. 3 DATABASE AND DATABASE MANAGEMENT SYSTEMS The database is now the underlying framework of the information system and has fundamentally changed the way many companies and individuals work. In today's technology-intensive economy, most organizations around the world- whether they are for - profit, not -for-profit, educational or governmental - could not stay competitive or achieve their goals without database management systems. Databases touch all aspects of our lives (in fact, the database is now such an integral part of our day-to-day life that often we're not aware we are using one). Users of a database store crucial information - from customers names and suppliers prices to sales history and procurement records - update that information and make it readily available to whoever needs it. People who work with databases are responsible for many of the benefits that computers have offered all kinds of organizations. These are some examples of Database Applications: • Banking: all transactions • Airlines: reservations, schedules • Universities: registration, grades • Sales: customers, products, purchases • Manufacturing: production, inventory, orders, supply chain • Human resources: employee records, salaries, tax deductions FILE-BASED APPROACH In the early days, database applications were built on top of file systems. That's the traditional way to use computers to back information systems: to store data in files and process them by means of dedicated programs. The file is a named collection of data regarding similar entities (objects, facts, events). Drawbacks of using file systems to store data: • Data redundancy and inconsistency: multiple file formats, duplication of information in different files • Difficulty in accessing data: need to write a new program to carry out each new task • Data isolation : multiple files and formats
  • 2. • Integrity problems : Integrity constraints become part of program 4 code, hard to add new constraints or change existing ones • Atomicity of updates: failures may leave database in an inconsistent state with partial updates carried out (E.g. transfer of funds from one account to another should either complete or not happen at all) • Concurrent access by multiple users : concurrent accessed needed for performance, uncontrolled concurrent accesses can lead to inconsistencies (E.g. two people reading a balance and updating it at the same time) • Security problems These disadvantages were especially pronounced in first and second-generation application systems. In third-generation systems, a number of powerful support packages and tools have been introduced to minimize some of the disadvantages. This software support provides data dictionaries, high-level programming languages. However, even with these facilities, there remain the fundamental deficiencies of file processing systems: redundant data, low sharing of data, lack of standards and control, and low productivity. To overcome these disadvantages, a new approach emerges in the years 70, the data base approach discussed in the following section. THE DATABASE APPROACH The database approach represents a different concept in information resource management. Data are viewed as an important, shared resource that must be managed like any other asset, such as people, materials, equipment and money. The data base concept is rooted in an attitude of sharing common data resources, releasing control of those data resources to a common responsible authority, and cooperating in the maintenance of those shared data resources. The database A database consists of a shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. The database system provides the organization with centralized control of its data. Such a situation contrasts sharply with that found in an enterprise without a database system, where typically each application has its own private files, so that the data is widely dispersed and might thus be difficult to control in any systematic way.
  • 3. The database is a single, possibly large repository of data, which can be used simultaneously by many departments and users. All data that is required by these users is integrated with the minimum amount of duplication. And, importantly, the database is normally not owned by any one department or user but is a shared corporate resource. Technically, the database approach differs from the file approach by the following features: • permanent links are established between files to materialize real life interactions. From here, the technical definition is derived: Database is a named collection of interrelated files, shared by more users. • data descriptions (logical records of each file) are stored on magnetic support (not in programs but in data files or close). As well as holding the organization's operational data, the database also hold a description of this data. For this reason, a database is also defined as a self-describing collection of integrated records. The description of data (the meta-data) is known as the system catalog or data dictionary. It is the self-describing nature of a database that provides what's known as data independence. This means that the programs consist only on algorithms that are no more data dependent (we can use the same program for more data descriptions) and they use the data description in common. 5 Program Program Data description Algorithm Algorithm Data Description Data Data File approach Data base approach Fig. 2.1 File and database approaches The concept of centralized control implies there will be some identifiable person who has this central responsibility for the data. That person is the data administrator (DA). It is the data administrator’s job to decide what data should be stored in the database in the first place, and to establish policies for maintaining and dealing with that data once it has
  • 4. been stored. The technical person responsible for implementing the data administrator’s decisions is the database administrator (DBA). 6 Data base management system (DBMS) The DBMS is a software system that enables users to define, create and maintain the database and also provides controlled access to the database. So, the DBMS is the software that interacts with the users, application programs and the database. A database management system (DBMS) is the software used to specify the logical organization for a database and access it. DBMS provides an environment that is both convenient and efficient to use. Application programs Users interact with the database through a number of application programs that are used to create and maintain the database and to generate information. These programs can be conventional batch applications or, more typically nowadays, they will be online applications. The application programs may be written in some programming language or in some higher-level fourth-generation language. An application program is a computer program that interacts with the database by issuing an appropriate request to the DBMS. Views A DBMS provides a facility known as a view mechanism, which allow each user to have his or her own customized view of the database, where a view is some subset of the database. A view is a virtual table that does not necessarily exist in the database but is generated by the DBMS from the underlying base tables whenever it's accessed. A view is usually defined as a query that operates on the base tables to produce another virtual table. As well as reducing complexity by letting users see the data in the way they want to see it, views have several other benefits: - Views provide a level of security. Views can set up to exclude data that some users should not see. - Views provide a mechanism to customize the appearance of the database.
  • 5. - A view can present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed. Components of the DBMS environment We can identify five major components in the DBMS environment: 1. Hardware - the computer systems that the DBMS and the application programs run on. This can change from a single PC, to a single mainframe, to a network of computers. 2. Software - the DBMS software and the application programs, together with the operating system, including network software if the DBMS is being used over a network. 3. Data and data descriptions (meta-data) - the data acts like a bridge between the hardware and software components and the human components. 4. Procedures - the instructions and rules that govern the design and use 7 of the database. 5. People - In the database environment, human jobs are more specific: some users deal only with data retrieving (end users), some with developing new information system (application programmers) and some must manage the complex data base environment (data administrator and database administrator). Also, there are other specialists, like database designers (software professionals who specify information, content and create database systems), Web-application developers (create Web pages and devise means for processing information content through the Web) or Web-site designers.
  • 6. 8 . End Users DBMS group FMS Programmers Operating System Database Administrator BIOS Database Data dictionary and directory Fig 2.2 Software environment in database approach All data handling (storing, updating or retrieving) is done only by the DBMS. Some database uses the File Management System to store, update and retrieve data in files visible from the Operating system (Dbase, Fox, Paradox). Modern DBMS like Microsoft Access and Oracle don’t use the File Management System, they had their own routines of storing data in tables enclosed in a container seen as a unique file by the Operating System. Sometimes, the DBMS replace totally the FMS and sometimes the DBMS is embedded in the Operating System. DBMS architectures Before the advent of the Web, generally a DBMS would be divided in two parts: • a client program that handles the main business and data processing logic and interfaces with the user; • a server program (sometimes called the DBMS engine) that manages and controls access to the database. This is known as a two-tier client-server architecture.
  • 7. In the mid -1990s, as applications became more complex and potentially could be developed to hundreds and thousands of end-users, the client side of this architecture gave rise to two problems: ü A "fat" client, requiring considerable resources on the client's 9 computer to run effectively (disk space, RAM and CPU power). ü A significant client-side administration overhead. By 1995, a new variation of the traditional two-tier client-server model appeared to solve these problems, called three-tier client-server architecture. This new architecture proposed three layers, each potentially running on a different platform: • The user interface layer, which runs on the end-user's computer (the client). • The business logic and data processing layer - a middle layer which runs on a server and is often called the application server. One application server is designed to serve multiple clients. • A DBMS, which stores the data required by the middle layer. This tier may run on a separate server called the database server. The three-tier design has many advantages over the traditional two-tier design, such as: ü A "thin" client, which requires less expensive hardware. ü Simplified application maintenance, as a result of centralizing the business logic for many end-users into a single application server. ü Added modularity, which makes it easier to modify or replace one tier without affecting the other tiers. ü Easier load balancing, as a result of separating the core business logic from the database functions. A Transaction Processing Monitor (TPM) -a program that controls data transfer between clients and servers in order to provide a consistent environment for Online Transaction Processing) can be used to reduce the number of connections to the database server. ü It maps quite naturally to the Web environment, with a Web browser acting as the "thin" client, and a Web server acting as the application server.
  • 8. 10 Functions of a DBMS A good DBMS should furnish a number of capabilities. The list of features that a DBMS should furnish includes the following: 1. Data storage, retrieval and update: the ability to store, retrieve, and update the data that is in the database - the fundamental function of a DBMS. Unless a DBMS provides this facility, further discussion of what a DBMS can do is irrelevant. In storing, updating, and retrieving data, it should not be incumbent upon the user to be aware of the system's internal structures or the procedures used to manipulate these structures. This manipulation is strictly the responsibility of the DBMS 2. Meta-data storage, retrieval and update: A user-accessible catalog in which descriptions of data items are stored and which is accessible to users. A key feature of a DBMS is the provision of an integrated system catalog to hold data about the structure of the database, users, applications, and so on. The catalog is expected to be accessible to users as well as to the DBMS. Typically, the system catalog stores: - names, types and sizes of data items, - integrity constraints on the data, - names of authorized users who have access to data. 3. Transaction support. A transaction can be defined as being an action, or series of actions, carried out by a single user or application program, which access or changes the contents of the database. For example, a simple transaction will be to add a new customer in the database, to update the price of one product or a more complex one to delete a sale agent and to reassign his customers to others sales agents. If the transaction fails during execution, the database should be in inconsistent state: some changes will have been made and others not. To overcame this, a DBMS should provide a mechanism that will ensure either that all the updates corresponding to a given transaction are made or that none of them are made. We can use the famous "ACID test" when deciding whether or not a database management system is adequate for handling transactions. An adequate system has the following properties:
  • 9. ü Atomicity: results of a transaction's execution are either all committed 11 or all rolled back. All changes take effect, or none do. . ü Consistency: the database is transformed from one valid state to another valid state. This defines a transaction as legal only if it obeys user-defined integrity constraints. Illegal transactions aren't allowed and, if an integrity constraint can't be satisfied then the transaction is rolled back. ü Isolation: the results of a transaction are invisible to other transactions until the transaction is complete. ü Durability: once committed (completed), the results of a transaction are permanent and survive future system and media failures. 4. Concurrency control services (support for shared update): a mechanism to ensure accuracy when several users are updating the database at the same time. Concurrent access is relatively easy if all users are only reading data, as there is no way they can interfere with one another. When two or more users are accessing the database simultaneously and at least one of them is updating data, there may be interference that can result in inconsistencies. One approach that ensures correct results is locking; as long as a portion of the database is locked by one user, other users cannot gain access to it. 5. Recovery services: a mechanism for recovering the database in the event that the database is damaged in any way. This may be the result of a system crash, media failure, a hardware or software error causing the DBMS to stop, or it may be the result of the user detecting an error during the transaction and aborting the transaction before it completes. In all the cases, the DBMS must provide a mechanism to recover the database to a consistent state. The simplest approach to recovery involves periodically making a copy of the database (called a backup or a save). If a problem occurs, the database is recovered by copying this backup copy over it. In effect, the damage is undone by returning the database to the state it was in when the last backup was made. 6. Security services: a mechanism to ensure that only authorized users can access the database. A DBMS must furnish a mechanism that restricts access to the database to authorized users. The term security
  • 10. refers to the protection of the database against unauthorized (or even illegal) access, either intentional or accidental. 7. Integrity services: mechanisms to ensure that certain rules are followed with regard to data in the database and any changes that are made in the data. Data integrity refers to the correctness and consistency of stored data. It can be considered as another type of database protection. While it's related to security, it has wider implications; integrity is concerned with the quality of data itself. Integrity is usually expressed in terms of constraints, which are consistency rules that the database is not permitted to violate. The types of constraints that may be present fall into the following four categories: § Data type. The data entered for any column should be consistent with the data type for that column. For a numeric column, only numbers should be allowed to be entered. If the column is a date, only a legitimate date (in the form MMDDYY or MM/DD/YY) should be permitted. § Legal values. It may be that for certain columns, not every possible value that is of the right type is legitimate. For example, even though CREDLIM is a numeric column, only the values 400, 500, 700, 800, and 1,000 may be valid. § Format. It may be that certain columns have a very special format that 12 must be followed. § Key constraints. There are two types of key constraints: primary key constraints and foreign key constraints. Primary key constraints enforce the uniqueness of the primary key. For example, forbidding the addition of a customer whose number matched the number of a customer already in the database would be a primary key constraint. Foreign key constraints enforce the fact that a value for a foreign key must match the value of the primary key for some row in another table. Forbidding the addition of a customer whose sales agent was not already in the database would be an example of a foreign key constraint. An integrity constraint can be treated in one of four ways: a) The constraint can be ignored, in which case no attempt is made to enforce the constraint. b) The burden of enforcing the constraint can be placed on the users of the system. This means that users must be careful that any changes they make in the database do not violate the constraint.
  • 11. c) The burden can be placed on programmers. Logic to enforce the constraint is then built into programs. Users must update the database only by means of these programs and not through any of the built-in entry facilities provided by the DBMS, since these would allow violation of the constraint. The programs are designed to reject any attempt on the part of the user to update the database in such a way that the constraint is violated. d) The burden can be placed on the DBMS. The constraint is specified to the DBMS, which then rejects any attempt to update the database in such a way that the constraint is violated. The best approach is the last one. Unfortunately, most DBMS don't have all the necessary capabilities to enforce the various types of integrity. Usually, the approach that is taken is a combination of the (c) and (d) in the foregoing list. We let the DBMS enforce any of the constraints that it is capable of enforcing; application programs enforce other constraints. We might also create a special program whose sole purpose would be to examine the data in the database to determine whether any constraints had been violated; this program would be run periodically. Corrective action could be taken to remedy any violations that were discovered by leans of this program. 8. Support for data communication. Most users access the database from terminals. Sometimes, these terminals are connected directly to the computer hosting the DBMS. In other cases, the terminals are at remote locations and communicate with the computer hosting the DBMS over a network. In either case, the DBMS must be capable of integrating with networking/communication software, 9. Services to promote data independence: facilities to support the independence of programs from the structure of the database. One of the advantages of working with a DBMS is data independence; that is, the property that changes can be made in the layout of a database without application programs necessarily being affected. Data independence is normally achieved through a view mechanism; there are usually several types of changes that can be made to the physical characteristics of the database without affecting the views, such as using different file organizations or modifying indexes - this is called physical data independence. However, complete logical data independence is more difficult to achieve; the addition of a new file or 13
  • 12. field can usually be accommodated, but not their removal (in some systems, any type of change to a file structure is prohibited). 10. Utility services: DBMS-provided services that assist in the general maintenance of the database. Utility programs help the Database Administrator to manage the database effectively. Following is a list of such services that may be provided by a DBMS. • Services that permit changes to be made in the database structure (adding new tables or columns, deleting existing tables or columns, changing the name or characteristics of a column, and so on). • Services that permit the addition of new indexes and the deletion of 14 indexes that are no longer wanted. • Import and export facilities from other software products. For example, these services allow data to be transferred in a relatively easy fashion between the DBMS and a spreadsheet, word processing, or graphics program, or to load and unload data from or to flat files. • Monitoring facilities, to monitor database usage and operation. • Several of the services that form a part of the fourth-generation environment are also furnished by some of the better DBMS. These include such things as easy-to-use edit and query capabilities, screen generators, report generators, and so on. • Access to both procedural and nonprocedural languages. • An easy-to-use graphical user interface that allows users to tap the power of the DBMS without having to resort to a complicated set of commands. The actual level of functionality offered by a DBMS differs from product to product. For example, a DBMS for a PC may not support concurrent shared access, and it may only provide limited security, integrity and recovery control. Modern, large multi-user DBMS products offer all the above functions and much more. DATABASE ADMINISTRATION AND SECURITY Data administration and database administration The Data Administrator (DA) and Database Administrator (DBA) are responsible for managing and controlling the activities associated with the corporate data and the corporate database, respectively. Depending on
  • 13. the size and complexity of the organization and database system, the DA and DBA can be the responsibility of one or more people. Data administration - the management and control of the corporate data, including database planning, development and maintenance of standards, policies and procedures, and logical database design. The DA is responsible for the corporate data, which includes non-computerized data, and in practice is often concerned with managing the shared data of users or business application areas of an organization. He must ensure that the application of database technologies supports the corporate objectives. Database administration - the management and control of the corporate database system, including physical database design and implementation, setting security and integrity controls, monitoring system performance, and reorganizing the database as necessary. The DBA is more technically oriented than the DA, requiring knowledge of specific DBMSs and the operating system environment. The primary responsibilities of the DBA are centered on developing and maintaining systems using the DBMS software to its full extent. In some organizations, data administration is a distinct business 15 area, in others it may be combined with database administration. Data administration Database administration Involved in strategic IS planning Evaluates new DBMSs Determines long-term goals Executes plans to achieve goals Determines standards, policies and procedures Enforces standards, policies and procedures Determined data requirements Implements data requirements Develops logical database design Develops physical database design Develops and maintains corporate data model Implements physical database design Coordinates database development Monitors and controls database use Managerial orientation Technical orientation DBMS independent DBMS dependent Database security Database security is the mechanism that protect the database against intentional or accidental threats. Database security encompasses hardware, software, people and data. This need for security is due to the increasing amounts of crucial corporate data being stored on computer and the
  • 14. acceptance that any loss or unavailability of this data could be potentially disastrous. A database represents nowadays an essential corporate resource that should be properly secured using appropriate controls. Database security is considered in relation to the following outcomes: - theft and fraud, - loss of confidentiality (secrecy), - loss of privacy, - loss of integrity, - loss of availability. An organization needs to identify the types of threats it may be subjected to (we understand by threats any situations or events, whether intentional or unintentional, that may adversely affect a system and consequently the organization) and initiate appropriate plans and countermeasures, considering also the costs of implementing them. The types of countermeasures to threats on database systems range from physical controls to administrative procedures. Despite the range of computer-based controls that are available, generally, the security of a DBMS is only as good as that of the operating system, owing to their close association. The most widely used computer-based security controls for a multi-user environment are: 1) Authorization (access control) - the granting of a right or privilege that enables a subject to have legitimate access to a database system or a database system's object. The process of authorization involves authentication (a mechanism that determines whether a user is who he or she claims to be) of a subject (a user) requesting access to an object (a database table, view, procedure or any other object that can be created within the database system). A system administrator is usually responsible for permitting user's access, by creating individual users accounts and passwords. Once a user is given permission to use a DBMS, various other privileges may also be automatically associated with it. Privileges are granted to users to accomplish the tasks required for their jobs. 2) Views - virtual tables that does not necessarily exist in the database but can be produced upon request by a particular user, at the time of request. The view mechanism provides a powerful and flexible security mechanism by hiding parts of the database from certain users. 16
  • 15. 3) Backup and recovery - the process of periodically taking a copy of the database and log file (and possibly programs) onto offline storage media in order to assist the recovery of the database following failure. 4) To keep track of database transactions, the DBMS maintains a special file called a log file (or journal) that contains information about all updates to the database. A DBMS should provide logging facilities, sometimes referred to as journaling, which keep track of the current state of transactions and database changes, to provide support for recovery procedures. 5) Integrity -integrity constraints contribute to maintaining a secure database system by preventing data from becoming invalid, and hence giving misleading or incorrect results. 6) Encryption - the encoding of the data by a special algorithm that renders the data unreadable by any program without the decryption key. 7) Redundant Array of Independent Disks (RAID) - the hardware that DBMS is running on must be fault-tolerant, meaning that the DBMS should continue to operate even if one of the hardware components fails. RAID technology works by having a large disk array comprising an arrangement of several independent disks that are organized to improve reliability and at the same time to increase performance. 17 DATABASE APPROACH - ADVANTAGES AND DISADVANTAGES The main benefits of the database approach are: 1. Control of data redundancy The database approach eliminates redundancy where possible; previously separate (and redundant) data files are integrated into a single, logical structure. In addition, each data item occurrence is ideally recorded in only one place in the database. That doesn’t mean that all redundancy can or should be eliminated. Sometimes there are valid reasons for storing
  • 16. multiple copies of the same data. However, the amount of redundancy inherent in the database is controlled. 18 2. Data consistency By controlling (or eliminating) data redundancy, we greatly reduce the risk of inconsistencies occurring. If data is stored only once in the database, any update to it's value has to be performed only once and the new value is immediately available to all users. When controlled redundancy is permitted in the database, the database system itself should enforce consistency by updating each occurrence of a data item when a change occurs – that means that the DBMS could guarantee that the database is never inconsistent as seen by the user, by ensuring that any change made to either of the two entities is automatically applied to the other one also (process known as “propagating updates”). However, few commercially available systems today are capable of automatically propagating updates in this manner; most current products do not support controlled redundancy at all, except in certain special situations. 3. Sharing of data In a file-based approach, typically files are owned by the people or departments that use them. On the other hand, the database belongs to the entire organization and can be shared by all authorized users. Sharing means not only that existing applications can share the data in the database, but also that new applications can be developed to operate against that same stored data. In other words, it might be possible to satisfy the data requirements of new applications without having to create any additional stored data. The new applications can also rely on the functions provided by the DBMS, such as data definition and manipulation, concurrency and recovery control, rather than having to provide these functions themselves. 4. Improved data integrity The problem of integrity is the problem of ensuring that the data in the database is accurate. Database integrity is usually expressed in terms of constraints, which are consistency rules that the database is not permitted to violate. Inconsistency between two entries that purport to represent the same “fact” is an example of lack of integrity; that particular problem can arise only if redundancy exists in the stored data. Even if there is no redundancy, however, the database might still contain incorrect information.
  • 17. Centralized control of the database can help in avoiding such problems – insofar as they can be avoided – by permitting the data administrator to define (and the DBA to implement) integrity rules to be checked whenever any data update operation is attempted. It is worth pointing out that data integrity is even more important in a multi-user database than it is in a “private files” environment, precisely because the database is shared. For without appropriate controls it would be possible for one user to update the database incorrectly, thereby generating bad data and so “infecting” other innocent users of that data. 19 5. Standards can be enforced Establishing the data administration function is an important part of the database approach. This organizational function has authority for defining and enforcing data standards. With central control of the database, data base administrator can ensure that all applicable standards are observed in the representation of the data. Applicable standards might include any or all of the following: corporate, installation, departmental, industry, national and international standards. Standardizing data representation is particularly desirable as an aid to data interchange, or migration of data between systems. Likewise, data naming and documentation standards are also very desirable as an aid to data sharing and understandability. 6. Improved security The data administration function has complete jurisdiction over the database and is responsible for establishing controls for accessing, updating and protecting data. The DBA can ensure that the only means of access to the database is through the proper channels, and hence can define security rules to be checked whenever access is attempted to sensitive data. Different rules can be established for each type of access to each piece of information in the database. Without such rules the security of data might actually be more at risk than in a traditional (dispersed) filing system; centralized nature of a database system in a sense requires that a good security system be in place also. 7. Conflicting requirements can be balanced Knowing the overall requirements of the organization – as opposed to the requirements of individual users – the DBA can so structure the system as to provide an overall service that is “best for the organization”. For example, a representation can be chosen for the data in storage that gives
  • 18. fast access for the most important applications (possibly at the cost of poorer performance for certain other applications). 20 8. Increased productivity A major advantage of the database approach is that the cost and time for developing new business applications are greatly reduced. Once the database has been designed and implemented, a programmer can code and debug a new application at least two to four times faster than with conventional data files; the reason for this improvement is that the programmer is no longer saddled with the burden of designing, building and maintaining master files. 9. The provision of data independence Applications implemented on older systems tend to be data-depended. What this means is that the way in which the data is organized in secondary storage, and the technique for accessing it, are both dictated by the requirements of the application under consideration, and moreover that knowledge of that data organization and that access technique is built into the application logic and code. It is impossible to change the storage structure (how the data is physically stored) or access technique (how it is accessed) without affecting the application, probably drastically. In a database system, however, it would be extremely undesirable to allow applications to be data-dependent, for at least the following two reasons: • Different applications will need different views of the same data • The DBA must have the freedom to change the storage structure or access technique in response to changing requirements, without having to modify existing applications. For example, new kinds of data might be added to the database; new standards might be adopted; application priorities might change; new types of storage device might become available; and so on. If applications are data-depended, such changes will typically require corresponding changes to be made to programs, thus typing out programmer effort that would otherwise be available for the creation of new applications. It follows that the provision of data independence is a major objective of database systems. Data independence can be defined as the immunity of applications to change in storage structure and access technique. The database should be able to grow without affecting existing applications; that is probably the single most important reason for requiring data independence in the first place.
  • 19. However, data independence is not an absolute – different systems provide it in different degrees; in fact, few systems, if any, provide no data independence at all – it is just that some systems are less data-dependent than others. There are, however, some disadvantages of the database approach, such as: 1. Complexity. A DBMS is an extremely complex piece of software, and all users (database designers and developers, database administrators and end-users) must understand the DBMS functionality to take full advantage of it. 2. Cost of DBMS. The cost of DBMS varies significantly, depending on the environment and functionality provided. There is also the recurrent annual maintenance cost, which is a percentage of the list price. 3. Cost of conversion. In some situations, the cost of the DBMS and extra hardware may be insignificant compared with the cost of converting existing applications to run on the new DBMS and hardware. This cost is one of the main reasons why some companies feel tied with their current systems and cannot switch to more modern database technology. 4. Performance. Typically, a file-based system is written for a specific application, such as invoicing. As a result, performance is generally very good. A DBMS is written to be more general, to cater for many applications rather that just one. The effect is that some applications may not run as fast using a DBMS as they did before. 5. Higher impact of a failure. The centralization of resources increases the vulnerability of the system. Since all users and applications rely on the availability of the DBMS, the failure of any component can bring operations to a complete halt until the failure is repaired. 21