Tuning Repository Performance
The PowerMart and
PowerCenter repository has more than 80 tables and almost all tables use one or
more indexes to speed up queries. Most databases keep and use column
distribution statistics to determine which index to use to execute SQL queries
optimally. Database servers do not update these statistics continuously.
In frequently-used
repositories, these statistics can become outdated very quickly and SQL query
optimizers may choose a less than optimal query plan. In large repositories,
the impact of choosing a sub-optimal query plan can affect performance
drastically. Over time, the repository becomes slower and slower.
To optimize SQL
queries, you might update these statistics regularly. The frequency of updating
statistics depends on how heavily the repository is used. Updating statistics
is done table by table. The database administrator can create scripts to
automate the task.
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