Queries and the query optimizer

These topics describe query plans, explain how the database server manages query optimization, and discuss factors that you can use to influence the query plan. These topics also describe performance considerations for SPL routines, the UDR cache, and triggers.

The parallel database query (PDQ) features in the database server provide the largest potential performance improvements for a query. Parallel database query (PDQ) describes PDQ and the Memory Grant Manager (MGM) and explains how to control resource use by queries.

PDQ provides the most substantial performance gains if you fragment your tables as described in Fragmentation guidelines.

Improving individual query performance explains how to improve the performance of specific queries.

Data warehouse queries and performance issues related to dimensional databases are described in the IBM® Informix Data Warehouse Guide.

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