It’s been said that the database administrator, or DBA, has
three basic tasks. In decreasing order
of importance, they are: protect the
data, protect the data, and protect the data.

Although data integrity is clearly the #1 job — who cares if
the database is available or fast if the data isn’t good — the DBA has many
other jobs as well.

The Interview Questions in this Hiring Kit have been
developed around the actual tasks that a DBA performs, as described below. Some
duties are common to all DBAs, and others are only required in some database
environments.

General tasks

  • Installation,
    configuration, upgrade, and migration –     Although system administrators are
    generally responsible for the hardware and operating system on a given server,
    installation of the database software is typically up to the DBA. This job role
    requires knowledge of the hardware prerequisites for an efficient database
    server, and communicating those requirements to the system administrator. The
    DBA then installs the database software and selects from various options in the
    product to configure it for the purpose it is being deployed. As new releases
    and patches are developed, it’s the DBA’s job to decide which are appropriate
    and to install them. And finally, if this server is a replacement for an
    existing one, it’s the DBA’s job to get the data from the old server to the new
    one.
  • Backup
    and Recovery –     DBAs are responsible for developing, implementing, and
    periodically testing a backup and recovery plan for the databases they manage.
    Even in large shops where a separate system administrator performs server
    backups, the DBA has final responsibility for making sure that the backups are
    being done as scheduled and that they include all the files needed to make database
    recovery possible after a failure. When failures do occur, the DBA needs to know how to use the backups to return
    the database to operational status as quickly as possible, without losing any
    transactions that were committed. There are several ways the database can fail,
    and the DBA must have a strategy to recover from each. From a business
    standpoint, there is a cost to doing backups, and the DBA makes management
    aware of the cost/risk tradeoffs of various backup methods.
  • Database
    Security –     Because databases centralize the storage of data, they are
    attractive targets for hackers and even curious employees. The DBA must
    understand the particular security model that the database product uses, and
    how to use it effectively to control access to the data. The three basic
    security tasks are authentication (setting up user accounts to control logins
    to the database), authorization (setting permissions on various parts of the
    database), and auditing (tracking who did what with the database). The auditing task is particularly important currently, as regulatory laws like
    Sarbanes-Oxley and HIPPA have reporting requirements that must be met.
  • Storage
    and Capacity Planning –     The primary purpose of a database is to store and
    retrieve data, so planning how much disk storage will be required and
    monitoring available disk space are key DBA responsibilities. Watching growth
    trends are important so that the DBA can advise management on long-term
    capacity plans.
  • Performance
    Monitoring and Tuning –     The DBA is responsible for monitoring the database
    server on a regular basis to identify bottlenecks — parts of the system that
    are slowing down processing — and remedy them. Tuning a database server is
    done on multiple levels. The capacity of the server hardware and the way the
    operating system is configured can become limiting factors, as can the database
    software configuration. The way the database is physically laid out on the disk
    drives and the types of indexing chosen also have an effect. Finally, the way
    queries against the database are coded can dramatically change how fast results
    are returned. A DBA needs to understand which monitoring tools are available at
    each of these levels and how to use them to tune the system. Proactive tuning is an attitude of designing performance into an application
    from the start, rather than waiting for problems to occur and fixing them. It requires
    working closely with developers of applications that run against the database,
    to make sure that best practices are followed so good performance will result.
  • Troubleshooting
    –     When things do go wrong with the database server, the DBA needs to know
    how to quickly ascertain the problem, and to correct it without losing data or
    making the situation worse.

Special Environments

In addition to these basic responsibilities, some DBAs need
special skills because of how the database is being used.

  • High
    Availability –     With the advent of the Internet, many databases that could
    have been available only during the day are now required to be available 24
    hours a day, 7 days a week. Websites have changed from static, pre-defined
    content to dynamically created content, using a database to create the page
    layout at the time a page is requested. If the website is available 24 x 7, so
    must the underlying database. Managing a database in this environment requires understanding of which types
    of maintenance operations can be done online (with the database available to
    users) and which must be scheduled for a maintenance “window” when the
    database may be shut down. It also requires planning for redundant hardware
    and/or software components, so that when one fails, others will keep the total
    system available to its users. Techniques like online backups, clustering, replication, and standby databases
    are all tools the DBA can use to ensure higher availability.
  • Very Large Databases
    (VLDBs) –     As companies have found more and more uses for database
    technology, they tend to save more data. Also, the type of data stored in
    databases has changed, from structured data in neat rows and columns, to
    unstructured data like documents, images, sound files, and even fingerprints. Both
    trends have the same result: larger databases. Managing a very large database requires special skills of the DBA. The time
    required to do simple operations like copying a table can be prohibitive unless
    done correctly. The DBA needs to understand techniques like table partitioning
    (Oracle), federated databases (SQL Server), or replication (MySQL) to enable a
    database to scale to large sizes while still being manageable.
  • Data Extraction,
    Transformation, and Loading (ETL) –     In data warehouse environments, a key
    task is efficiently loading the data warehouse or data mart with large volumes
    of data extracted from multiple existing production systems. Often these
    production systems have different formats than the standardized definitions in
    the data warehouse, so data must be transformed (or “cleansed”)
    before loading. Extracting the data may or may not be the DBA’s responsibility
    in a given company, but making sure what is extracted is useful is, and the DBA
    is a key part of the team.

The Bottom Line

Increasing feature sets in popular database products have
steadily increased the number of things a DBA has to master. By checking for
skills in the above key areas, you can make sure the DBA you hire is up to the
task.