PDQPRIORITY environment variable

The PDQPRIORITY environment variable determines the degree of parallelism that the database server uses and affects how the database server allocates resources, including memory, processors, and disk reads.

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Is an integer in the range 0 to 100. The value 1 is the same as LOW, and 100 is the same as HIGH. Values lower than 0 are set to 0 (OFF), and values greater than 100 are set to 100 (HIGH).

Value 0 is the same as OFF (for HCL Informix® only).

Here the HIGH, LOW, and OFF keywords have the following effects:

When the database server allocates resources among all users, it gives as many resources as possible to the query.
Data values are fetched from fragmented tables in parallel.
PDQ processing is turned off (for HCL Informix only).

Usually, the more resources a database server uses, the better its performance for a given query. If the server uses too many resources, however, contention for the resources can take resources away from other queries, resulting in degraded performance. For more information about performance considerations for PDQPRIORITY, see the IBM® Informix Performance Guide.

An application can override the setting of this environment variable when it issues the SQL statement SET PDQPRIORITY, as the IBM Informix Guide to SQL: Syntax describes.

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