Functions of Data Base Administrator
Data Base Administrator (DBA) is a person or group in charge for implementing DBMS in an organization. Database Administrator's job requires a high degree of technical expertise and the ability to understand and interpret management requirements ata senior level. In practice the DBA may consist of team of people rather than just one person
The main responsibilities of DBA are:
• Makes decisions concerning the content of the database: It is the DBA's job to decide exactly what information is to be held in the database-in other words, to identify the' entities of interest to the enterprise and to identify information to be recorded about those entitie .
• Plans storage structures and access strategies: The DBA must also decide how the data is to be represented in the database, and must specify the representation by writing the storage structure definition (using the internal data defination language).
In addition, the associated mapping between the storage structure definition and the conceptual schema must also be specified.
• Provides support to users: It is the responsibility of the DBA to provide support to the users, to ensure that the data they require is available, and to write the\ necessary external schemas (using the appropriate external data definition language).
In addition, the mapping between any given eA1ernal schema and the conceptual' schema must also be specified.
• Defines security and integrity checks: DBA is responsible for providing the authorization and authentication checks such that no malicious users can accessdatabase and it must remain protected. DBA must also ensure the integrity of the database.
• Interprets backup and recovery strategies: In the event of damage to any portion\ of the database-caused by human error, say, or a failure in the hardware or supporting operating system-it is essential to be able to repair the data concerned witl1 a minimum of delay and with as little effect as possible on the rest of the system.
The DBA must define and implement an appropriate recovery strategy to recover he database from all types of failures.
• Monitoring performance and responding to changes in requirements: The
DBA is responsible for so organizing the system as to get the performance that is "best for the enterprise," and for making the appropriate adjustments as requirements change.
The data manager is the central software component of the DBMS. It is sometimes referred to as the database control system. One of the functions of the data manager is to convert operations in the user's queries coming directly via the query processor or\ indirectly via an application program from the user's logical view to a physical file system. The data manager is responsible for interfacing with the file system as show. In addition, the tasks of enforcing constraints to maintain the consistency and integrity of the data, as well as its security, are also performed by the data manager. It is also the responsibility of the Data. Manager to provide the synchronization in the simultaneous operations performed by concurrent users and to maintain the backup and recovery operations.
Responsibility for the structure of the files and managing the file space rests with the file manager. It is also responsible for locating the block containing the required record, requesting this block from the disk manager, and transmitting the required record to the data manager as shown. The file manager can be implemented using an interface to the existing file subsystem provided by the operating system of the host computer or it can include a file subsystem written especially for the DBMS.
The disk manager is part of the operating system of the host computer and all physical input and output operations are performed by it. The disk manager transfers the block or page requested by the file manager so that the latter need not be concerned with the physical characteristics of the underlying storage media.