Data Management - Part VI (Database Administration)

The Database Administrator

The data administrator is the person who makes the strategic and policy decision regarding the data of the enterprise, and the database administrator is who provides the necessary technical support for implementing those decisions. Thus the DBA is responsible for the overall control of the system at a technical level. We can now describe some of the functions of the DBA in a little more detail. In general those functions will include the following.

Defining the conceptual schema:

It is the data administrator's job to decide exactly what is to be held in the database- In other words, to identify the entities of interest to enterprise and to identify the information to be recorded about those entities. This process is usually referred to as logical (sometimes conceptual) database design. Once the data administrator has thus decided the content of the database at an abstract level, DBA will then create the corresponding conceptual schema, using the conceptual DDL.

Defining the internal schema :

The DBA must also decide how the data is to be represented in the stored database design. Having done the physical design, the DBA must then create the corresponding storage structure definition, using the internal DDL. ln addition he/she must also define the associated mapping between the internal and conceptual schema. In practice, either the conceptual DDL or the internal DDL - most likely the former - will probably include the means for defining that mapping, but the two functions (creating the schema, defining the mapping) should be clearly separable. Like the conceptual, the internal schema and corresponding mapping will exist in both source and object form.

Liaising with users:

It is the business of the DBA to liaise with the users, to ensure that the data they require is available, and to write the necessary external schema, using the applicable external DDL. In addition, the mapping between any given external schema and the conceptual schema must also be defined. Other aspect of the user liaison function include consulting on application design, providing technical education, assisting with problem determination and resolution, and similar System- related professional services.

Defining security and integrity rules: The DBA should use the conceptual DDL for specifying such rules

Defining Back up and recovery procedures:

Once enterprise is committed to a database system, it becomes critically dependent on the successful operation of the system. 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 with minimum of delay and with as little effect as possible on the rest of the system. For example the availability of data that has not been damaged should ideally not be affected. The DBA must define and implement an appropriate recovery scheme involving, e.9., periodic unloading or dumping of the database to backup storage, and procedures for reloading the database from necessary from the most recent dump.

Monitoring performance and responding to changing requirements :

The DBA is responsible for organizing the system as to get the performance that is "best for the enterprise," and for making the appropriate adjustments as requirements change. For example , it might be necessary to recognize the stored database on a periodic basis to ensure that performance levels remain acceptable.