The document discusses the key components of a database management system (DBMS). It describes four types of DBMS users including naive users, online users, application programmers, and database administrators. It then explains two main facilities provided by DBMS: the data definition language used to define the database structure and the data manipulation language used to retrieve, insert, and modify data. Finally, it outlines the typical structure of a DBMS, including components like the DDL compiler, data manager, file manager, disk manager, query processor, and data dictionary.

1. COMPONENTS OF DBMS
 USERS
 DBMS FACILITIES
 STRUCTURE
 DATABASE ACCESS

2. 1) Classification of DBMS Users
•Naive Users : Users who need not be aware of the presence of
database system. e.g. User of the ATM machine
•Online Users : These users are aware of the presence of the
database system and may have acquired a certain amount of expertise
in the limited interaction they are permitted with the database.
•Application Programmer : Professional programmers who are
responsible for developing application program or user interface fall
into this category.
•Database Administrator : Centralized control of the database is
exerted by a person or group of persons under the supervision of a
high-level administrator. This person or group is referred to as the
Data Base Administrator (DBA).

3. Duties of DBA
 Defining the conceptual schema
 Defining the internal schema
 Liaising with users
 Defining security and integrity constraints
 Defining recovery procedures

4. 2) DBMS Facilities
Two main types of facilities are provided by
DBMS :
 The Data Definition Language : DBMS provide a facility
known as DDL which can be used to define the conceptual
and internal level of the database. This definition includes
all the entity sets and their associated attributes as well
as the relationship among the entity sets.
 The Data Manipulation Language : The language used
to manipulate data in the database is called data
manipulation language. Data Manipulation involves
retrieval of data from data base, insertion of new data into
the database, and deletion or modification of existing
data.

5. 3) Structure of DBMS
 DDL Compiler : The DDL compiler converts the data definition
statements into set of tables. These tables contains the metadata
concerning the database.
 Data Manager : The main function of data manager is to convert
operations in the user’s queries from the user’s logical view to a
physical file system. The task of enforcing constraints to maintain
consistency is also performed by data manager
 File Manager : It is responsible for locating the block containing
the required record, requesting this block from the disk manager
and transmitting the required record to data manager.
 Disk Manager : All physical input and output operations are
performed by it.

6. Structure of DBMS (contd.)
 Query Processor : The query processor is used to interpret the
online user’s query and convert it into an efficient series of
operations in a form capable of being sent to the data manager.
 Data Dictionary : Information pertaining to the structure and
usage of data contained in the database, the metadata, is
maintained in a data dictionary. The term system catalog also
describes this metadata. The data dictionary, which is a database
itself, documents the data.
 Access Aids : To improve the performance of a DBMS, a set of
access aids in the form of indexes are usually provided in a
database system.

7. Structure of DBMS (contd.)
Query
Processor
Data Manager
File Manager
Disk Manager
Data Base
User
Interface
DDL
Compiler
Naïve User Online User DBA

8. Database Access
User’s
Query
Response
to user
Request specific
record
Request specific
record
Request specific
block
Requested
block
Input/Output
Block
Block from
secondary
Storage
DatabaseUser Interface Data Manager File Manager Disk Manager