Adjust the amount of memory and disk space for UPDATE STATISTICS

When you execute the UPDATE STATISTICS statement, the database server uses memory and disk to sort and construct data distributions. You can affect the amount of memory and disk space available for UPDATE STATISTICS operations.

You can affect the amount of memory and disk space available for UPDATE STATISTICS with the following methods:
  • PDQ priority

    You can obtain more memory for sorting when you set PDQ priority greater than 0. The default value for PDQ priority is 0. To set PDQ priority, use either the PDQPRIORITY environment variable or the SQL statement SET PDQPRIORITY.

    For more information about PDQ priority, see The allocation of resources for parallel database queries.

  • DBUPSPACE environment variable

    You can use the DBUPSPACE environment variable to specify the amount of system disk space (and the amount of memory for sorting values) that UPDATE STATISTICS MEDIUM or UPDATE STATISTICS HIGH statements can use in each pass to construct column distributions. If you specify too small a value, the database server instead uses enough space to write the largest column to disk.

    For more information about this environment variable, see the Informix® Guide to SQL: Reference.