Advantages & Disadvantages of DBMS

Features / Advantages of DBMS:

1.      Self-Describing Nature:

A database system is referred to as self-describing because it not only contains the database itself, but also metadata which defines and describes the data and relationships between tables in the database. This information is used by the DBMS software or database users if needed. This separation of data and information about the data makes a database system totally different from the traditional file-based system in which the data definition is part of the application programs.

2.      Redundancy Control:

In non-database systems (traditional computer file processing), each application program has its own files. In this case, the duplicated copies of the same data are created at many places. In DBMS, all the data of an organization is integrated into a single database. The data is recorded at only one place in the database and it is not duplicated.

3.      Elimination of inconsistency:

When the same data is duplicated and changes are made at one site, which is not propagated to the other site, it gives rise to inconsistency and the two entries regarding the same data will not agree. At such times the data is said to be inconsistent.

By controlling the data redundancy, the data inconsistency is eliminated. If a data item appears only once, any update to its value has to be performed only once and the updated value (new value of item) is immediately available to all users. 

4.      Sharing of Data:

In DBMS, data can be shared by authorized users of the organization. The database administrator manages the data and gives rights to users to access the data. Many users can be authorized to access the same piece of information simultaneously. The remote users can also share same data. Similarly, the data of same database can be shared between different application programs.

5.      Maintenance of Integrity:

Since DBMS is a central system, so standard can be enforced easily may be at Company level, Department level, National level or International level. The standardized data is very helpful during migration or interchanging of data.

6.      Control over Security:

Data security is the protection of the database from unauthorized users. Only the authorized persons are allowed to access the database. Some of the users may be allowed to access only a part of database i.e., the data that is related to them or related to their department.

DBMS allows different levels of access to different users based on their roles. In the school database, individual students will have access to their data alone, while their teachers will have access to all the students whom they are teaching and for the subjects that they are teaching. Class teacher will be able to see the reports of all the students in that class, but not other classes.

7.      Transaction Control / Data Atomicity:

DBMS makes sure either the transaction is fully complete or it is rolled back to the previous committed state. It does not allow the system to be in a partially committed state.

A transaction in commercial databases is referred to as atomic unit of work. For example, when you purchase something from a point of sale (POS) terminal, a number of tasks are performed such as;

·        Company stock is updated.

·        Amount is added in company's account.

·        Sales person's commission increases etc.

All these tasks collectively are called an atomic unit of work or transaction. These tasks must be completed in all; otherwise partially completed tasks are rolled back.

8.      Data Independence:

The separation of data structure of database from the application program that is used to access data from database is called data independence. In DBMS, database and application programs are separated from each other. The DBMS sits in between them. You can easily change the structure of database without modifying the application program.

9.      Concurrency Control:

DBMS provide access to multiple users to access the database at the same time. It has its own mechanism to have concurrency accesses and hence avoid any incorrect data in the system. For example, if both users attempt to perform update operation on the same record, then one may overwrite the values recorded by the other.

10.   Backup and Recovery:

In a computer file-based system, the user creates the backup of data regularly to protect the valuable data from damaging due to failures to the computer system or application program. It is a time consuming method, if volume of data is large. Most of the DBMSs provide the 'backup and recovery' sub-systems that automatically create the backup of data and restore data if required.

Disadvantages of DBMS:

1.      Complexity:

The provision of the functionality that is expected of a good DBMS makes the DBMS an extremely complex piece of software. Database designers, developers, database administrators and end-users must understand this functionality to take full advantage of it. Failure to understand the system can lead to bad design decisions, which can have serious consequences for an organization.

2.      Size:

The complexity and breadth of functionality makes the DBMS an extremely large piece of software, occupying many megabytes of disk space and requiring substantial amounts of memory to run efficiently.

3.      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 halt.

4.      Cost of DBMS:

The cost of DBMS varies significantly, depending on the environment and functionality provided. There is also the recurrent annual maintenance cost.

5.      Additional Hardware costs:

The disk storage requirements for the DBMS and the database may necessitate the purchase of additional storage space. Furthermore, to achieve the required performance it may be necessary to purchase a larger machine, perhaps even a machine dedicated to running the DBMS. The procurement of additional hardware results in further expenditure.

6.      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 organizations feel tied to their current systems and cannot switch to modern database technology.

-profshardulp.patil@gmail.com

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