The following parameters in the database server configuration file have a significant impact on CPU utilization:
The following sections describe how these configuration parameters affect performance. For more information about database server configuration parameters, see the IBM Informix: Dynamic Server Administrator's Reference.
The following environment variables affect CPU utilization:
The OPTCOMPIND environment variable, when set in the environment of a client application, indicates the preferred way to perform join operations. This variable overrides the value that the OPTCOMPIND configuration parameter sets. For details on how to select a preferred join method, see OPTCOMPIND.
The PDQPRIORITY environment variable, when set in the environment of a client application, places a limit on the percentage of CPU VP utilization, shared memory, and other resources that can be allocated to any query that the client starts.
A client can also use the SET PDQPRIORITY statement in SQL to set a value for PDQ priority. The actual percentage allocated to any query is subject to the factor that the MAX_PDQPRIORITY configuration parameter sets. For more information on how to limit resources that can be allocated to a query, see MAX_PDQPRIORITY.
PSORT_NPROCS, when set in the environment of a client application, indicates the number of parallel sort threads that the application can use. The database server imposes an upper limit of 10 sort threads per query for any application. For more information on parallel sorts and PSORT_NPROCS, see Configuring Dbspaces for Temporary Tables and Sort Files.
For more information about environment variables that affect Informix database servers, see the IBM Informix: Guide to SQL Reference.
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