MUIT411 ENTERPRISE PROGRAMMING Lecturer: George Afiriyie Gyamfi REVIEW OF COMPONENTS OF DBMS DISTRIBUTED DATABASE SYSTEMS (DDBMS)

REVIEW OF COMPONENTS OF DBMS

DISTRIBUTED DATABASE SYSTEMS (DDBMS)

Unit Objectives Software components of a DBMS. Meaning of client–server architecture and advantages of this type of architecture for a DBMS. Function and uses of Transaction Processing Monitors.

Software components of a DBMS.

Meaning of client–server architecture and advantages of this type of architecture for a DBMS.

Function and uses of Transaction Processing Monitors.

COMPONENTS OF DBMS A DBMS is partitioned into several software components or modules, each of which is assigned a specific operation. The operating system provides only basic services and the DBMS must be built on top. The design of the DBMS must take into account the interface between the DBMS and operating system.

A DBMS is partitioned into several software components or modules, each of which is assigned a specific operation.

The operating system provides only basic services and the DBMS must be built on top. The design of the DBMS must take into account the interface between the DBMS and operating system.

Components of a DBMS

COMPONENTS OF DBMS The diagram shows how the DBMS interfaces with other software components such as user queries and access methods (file management techniques for storing and retrieving data records).

The diagram shows how the DBMS interfaces with other software components such as user queries and access methods (file management techniques for storing and retrieving data records).

Components of Database Manager (DM) © Pearson Education Limited 1995, 2005

Multi-User DBMS Architectures Teleprocessing File-server Client-server

Teleprocessing

File-server

Client-server

Teleprocessing Traditional architecture. Single mainframe with a number of terminals attached. Trend is now towards downsizing.

Traditional architecture.

Single mainframe with a number of terminals attached.

Trend is now towards downsizing.

TELEPROCESSING Downsizing is replacing expensive mainframe computers with most-effective networks of personal computers that achieve the same or even better results. This trend has given rise to the next two architectures : file server and client server

Downsizing is replacing expensive mainframe computers with most-effective networks of personal computers that achieve the same or even better results.

This trend has given rise to the next two architectures : file server and client server

File-Server File-server is connected to several workstations across a network. Database resides on file-server. DBMS and applications run on each workstation. This approach generate a significant amount of network traffic, which can lead to performance problems Disadvantages include: Significant network traffic. Copy of DBMS on each workstation. Concurrency, recovery and integrity control more complex.

File-server is connected to several workstations across a network.

Database resides on file-server.

DBMS and applications run on each workstation.

This approach generate a significant amount of network traffic, which can lead to performance problems

Disadvantages include:

Significant network traffic.

Copy of DBMS on each workstation.

Concurrency, recovery and integrity control more complex.

File-Server Architecture

Traditional Two-Tier Client-Server Client (tier 1) manages user interface and runs applications. Server (tier 2) holds database and DBMS. Data-intensive business applications consist of 4 major components; Database, transaction logic, the business and data application logic, user interface. Advantages include: wider access to existing databases; increased performance; possible reduction in hardware costs; reduction in communication costs; increased consistency.

Client (tier 1) manages user interface and runs applications.

Server (tier 2) holds database and DBMS.

Data-intensive business applications consist of 4 major components;

Database, transaction logic, the business and data application logic, user interface.

Advantages include:

wider access to existing databases;

increased performance;

possible reduction in hardware costs;

reduction in communication costs;

increased consistency.

Traditional Two-Tier Client-Server

Traditional Two-Tier Client-Server

Traditional Two-Tier Client-Server Processing of information involves checking authorization, ensuring integrity, maintaining system catalog and performing query and update processing. In addition it provides concurrency and recovery control .

Processing of information involves checking authorization, ensuring integrity, maintaining system catalog and performing query and update processing. In addition it provides concurrency and recovery control .

Three-Tier Client-Server Client side presented two problems preventing true scalability: ‘ Fat’ client, requiring considerable resources on client’s computer to run effectively. This includes disk space, RAM and CPU power Significant client side administration overhead. By 1995, three layers proposed, each potentially running on a different platform.

Client side presented two problems preventing true scalability:

‘ Fat’ client, requiring considerable resources on client’s computer to run effectively. This includes disk space, RAM and CPU power

Significant client side administration overhead.

By 1995, three layers proposed, each potentially running on a different platform.

THREE-TIER CLIENT SERVER The user interface, which runs on the end-users computer (the client) The business logic and data processing layer. The middle tier runs on a server and its often called application server. A DBMS, which stores the data required by the middle tier. The tier may run on a separate server called the database server.

The user interface, which runs on the end-users computer (the client)

The business logic and data processing layer. The middle tier runs on a server and its often called application server.

A DBMS, which stores the data required by the middle tier. The tier may run on a separate server called the database server.

Three-Tier Client-Server Advantages: ‘ Thin’ client, requiring less expensive hardware. Application maintenance centralized. Easier to modify or replace one tier without affecting others. Separating business logic from database functions makes it easier to implement load balancing. Maps quite naturally to Web environment.

Advantages:

‘ Thin’ client, requiring less expensive hardware.

Application maintenance centralized.

Easier to modify or replace one tier without affecting others.

Separating business logic from database functions makes it easier to implement load balancing.

Maps quite naturally to Web environment.

Three-Tier Client-Server © Pearson Education Limited 1995, 2005

Transaction Processing Monitors Program that controls data transfer between clients and servers in order to provide a consistent environment, particularly for Online Transaction Processing (OLTP).

Program that controls data transfer between clients and servers in order to provide a consistent environment, particularly for Online Transaction Processing (OLTP).

TPM as middle tier of 3-tier client-server

Transaction Processing Monitors Advantages Transaction Routing : The TP Monitor can increase scalability by directing transactions to specific DBMS Managing Distributed Transaction: The TP Monitor can manage transactions that require access to data held in the multiple, possibly heterogeneous DBMSs

Advantages

Transaction Routing : The TP Monitor can increase scalability by directing transactions to specific DBMS

Managing Distributed Transaction: The TP Monitor can manage transactions that require access to data held in the multiple, possibly heterogeneous DBMSs

Transaction Processing Monitors Load Balancing :- The TP Monitor can balance client requests across multiple DBMS on one or more computers by directing client service calls to the least loaded server. Funneling: In environments with a large number of users, it may sometimes be difficult for all users to be logged on simultaneously to the DBMS. The DBMS can establish connections with the DBMSs as and when required, and can funnel user request through these connections.

Load Balancing :- The TP Monitor can balance client requests across multiple DBMS on one or more computers by directing client service calls to the least loaded server.

Funneling: In environments with a large number of users, it may sometimes be difficult for all users to be logged on simultaneously to the DBMS. The DBMS can establish connections with the DBMSs as and when required, and can funnel user request through these connections.

Transaction Processing Monitors Increased reliability: The TP Monitor acts as a transaction manager, performing necessary actions to maintain the consistency of the database, with the DBMS acting as a resource manager. If the DBMS fails, the TP Monitor may be able to resubmit the transaction to another DBMS or can hold the transaction until the DBMS becomes available again. The TP Monitor is used in environments where there is large volume of transactions.

Increased reliability: The TP Monitor acts as a transaction manager, performing necessary actions to maintain the consistency of the database, with the DBMS acting as a resource manager. If the DBMS fails, the TP Monitor may be able to resubmit the transaction to another DBMS or can hold the transaction until the DBMS becomes available again.

The TP Monitor is used in environments where there is large volume of transactions.