Data-distribution cache

The database server uses distribution statistics generated by the UPDATE STATISTICS statement in the MEDIUM or HIGH mode to determine the query plan with the lowest cost.

When the database server accesses the distribution statistics for a specific column the first time, it reads the distribution statistics from the sysdistrib system catalog table on disk and stores the statistics in the data-distribution cache. These statistics can then be read for the optimization of subsequent queries that access the column.

Performance improves if these statistics are efficiently stored and accessed from the data-distribution cache. You can configure the size of the data-distribution cache with the DS_HASHSIZE and DS_POOLSIZE configuration parameters. For information about changing the default size of the data-distribution cache, see the topics about queries and the query optimizer in your HCL Informix® Performance Guide.

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