Furthermore, many database administrators
and IT managers confess that maintenance tasks sometimes go awry, thus extending
planned downtime into unplanned downtime.
For these reasons, modern database administrators insist on performing maintenance operations
online whenever possible. With some databases, it is now possible to execute online
backups, table reorganization, reindexing, fault isolation, and so forth. This reduces planned
downtime, as well as the probability of that it may extend into unplanned downtime (Lumpkin,
2004). Furthermore, online maintenance enables database administrators to lightly adapt to
change, without waiting for a window of planned downtime.
Related to maintenance is the issue of configuration. In the early days of database management
systems, the smallest change of data structure or operating environment required
the database administrator to halt the database and restart it with new parameters. That is
unthinkable in today??™s fast changing business environment. Restart is a form of downtime.
Therefore, a database that supports dynamic reconfiguration is an important and integral
component of any high availability strategy.
High.Availability.Clusters
Hardware clusters with database servers are the preferred strategy for achieving the shortest
period for recovery after a hardware or database failure.
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