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Chapter 6. Automatic maintenance
Your DB2 product provides automatic maintenance capabilities for performing
database backups, and keeping statistics current as necessary.
Automatic database backup provides users with a solution to help ensure their
database is being backed up both properly and regularly, without either having to
worry about when to back up, or having any knowledge of the backup command.
Automatic statistics collection attempts to improve the performance of the database
by maintaining up-to-date table statistics. The goal is to allow the optimizer to
choose an access plan based on accurate statistics. Automatic statistics profiling
advises when and how to collect table statistics by detecting outdated, missing,
and incorrectly specified statistics and by generating statistical profiles based on
query feedback.
Enablement of the automatic maintenance features is controlled using the
automatic maintenance database configuration parameters. These are a hierarchical
set of switches to allow for simplicity and flexibility in managing the enablement
of these features.
The Configuration Advisor runs automatically when you create a database in DB2
Version 9. This autonomic computing feature provides significant performance
improvement to newly created databases, and causes little overhead to the system.
Also when you create a database in DB2 Version 9, AUTOMATIC STORAGE is
enabled by default. Automatic storage simplifies storage management by allowing
you to specify storage paths where the database manager can place table space
data, and where the database manager allocates space for various uses.
Self tuning memory is enabled by default, this autonomic feature simplifies the
task of memory configuration by automatically setting values for memory
configuration parameters and sizing buffer pools. When enabled, the memory
tuner dynamically distributes available memory resources between several memory
consumers including sort, package cache and lock list areas and buffer pools.
Automatic database backup
A database may become unusable due to a wide variety of hardware or software
failures. Automatic database backup simplifies database backup management tasks
for the DBA by always ensuring that a recent full backup of the database is
performed as needed. It determines the need to perform a backup operation based
on one or more of the following measures:
v You have never completed a full database backup
v The time elapsed since the last full backup is more than a specified number of
hours
v The transaction log space consumed since the last backup is more than a
specified number of 4 KB pages (in archive logging mode only).
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