Page 13 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Database Management Systems/Managing Database

Notes 5. Reduced Application Development Time: Since the DBMS provides several important
functions required by applications, such as concurrency control and crash recovery, high
level query facilities, etc., only application-specific code needs to be written.
6. Conflict Resolution: Since the database is under the control of the DBA, he should resolve
the conflicting requirements of various users and applications.

The DBA chooses the best file structure and access method to get optimal performance for
the response-critical applications, while permitting less critical applications to continue
to use the database, though with a relatively slower response.
7. Data Administration: By providing common base for a large collection of data that is
shared by several users, a DBMS facilitates maintenance and data administration tasks. A
good DBA can effectively ensure the fine-tuning, the data representation, periodic backups
etc.

8. Concurrent Access and Crash Recovery: A DBMS supports the notion of a transaction and
executes the actions of transactions in an interleaved fashion to obtain good performance,
but schedules them in such a way as to ensure that conflicting operations are not permitted
to proceed concurrently. Further, the DBMS maintains a continuous log of the changes to
the data, and if there is a system crash, it can restore the database to a transaction- consistent
state. That is, the actions of incomplete transactions are undone. Thus, if each complete
transaction, executing alone, maintains the consistent of criteria, then the database state
after recovery from a crash is consistent.

Task Discuss, what are the advantages of oracle instead of access.

1.5 Disadvantages of DBMS

The disadvantage of the DBMS system is overhead cost. The processing overhead introduced by
the DBMS to implement security, integrity, and sharing of the data causes a degradation of the
response and throughput times. An additional cost is that of migration from a traditionally
separate application environment to an integrated one.
Even though centralization reduces duplication, the lack of duplication requires that the database
be adequately backup so that in the case of failure the data can be recovered.
Backup and recovery operations are complex in a DBMS environment, and this is an increment
in a concurrent multi-user database system. A database system requires a certain amount of
controlled redundancies and duplication to enable access to related data items.
Centralization also means that the data is accessible from a single source, namely the database.
This increases the potential severity of security breaches and disrupting of the operation of the
organization because of down times and failures.

1.6 Database Architecture

The functional components of a database system can be broadly divided into query processor
components and storage manager components. The query processor includes:
1. DML Compiler: It translates DML statements in a query language into low-level instructions
that the query evaluation engine understands.

6 LOVELY PROFESSIONAL UNIVERSITY