Database administration: DBA staffing considerations |
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| 18 Nov 2005 | Written by Craig S. Mullins; Reprinted with permission from Addison Wesley |
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The following is an excerpt from Database Administration: The Complete Guide to Practices and Procedures.
How many DBAs?
One of the most difficult things to determine is the optimal number of database administrators (DBA)s required to keep an organization's databases online and operating efficiently. Many organizations try to operate with the minimal number of DBAsvon staff; the idea being that fewer database administration staff members lowers cost. However, that assumption may not be true. An overworked database administration staff can make mistakes that cause downtime and operational problems far in excess of the salary requirements of an additional DBA.
Determining how many DBAs is optimal is not a precise science. It depends on many
factors:
- Number of databases. The more databases that need to be supported, the more complex the job of database administration becomes. Each database needs to be designed, implemented, monitored for availability and performance, backed up, and administered. There is a limit to the number of databases that an individual DBA can control.
- Size of the databases. The larger the databases that need to be supported, the more difficult the job of database administration. A larger database takes longer to create, maintain, and tune. In addition, more potential for confusion arises when SQL takes longer to execute -- causing the DBA staff to spend more time working with developers to tune SQL.
- Number of users. As additional users are brought online, optimal database performance becomes more difficult to ensure. Additionally, as the number of users increases, the potential for increase in the volume of problems and calls increases, further complicating the DBA's job.
- Number of applications. A single database can be utilized by numerous applications. Indeed, one of the primary benefits of the DBMS is that it enables the sharing of data across an organization. As more applications are brought online, additional pressure is exerted on the database in terms of performance, availability, and resources. As more applications are brought online, more DBAs may be required to support the same number of databases.
- Service-level agreements (SLAs). The more restrictive the SLA, the more difficult it becomes for the DBA to deliver the service. For example, a service-level agreement requiring subsecond response time for transactions is
more difficult to support than an agreement requiring three-second response time.
- Availability requirements. Database administration becomes easier if databases have an allowable period of scheduled downtime. Some DBA tasks either require an outage, or are easier when an outage can be taken.
Considerations such as supporting e-business transactions and the Web drive the need for 24/7 database availability. 24/7 availability is often incompatible with certain DBA tasks.
- Impact of downtime. The greater the financial impact of an unavailable database, the greater the pressure on the DBA staff to assure greater database availability.
- Performance requirements. As the requirements for database access become more performance oriented, database administration becomes more complicated.
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