Informix Environment Variables

Environment variables that IBM Informix database server products and their utilities use.

DBDATE

The DBDATE environment variable specifies the end-user formats of DATE values. On UNIX systems that use the C shell, set DBDATE with this syntax.

DBPATH

The DBPATH environment variable identifies database servers that contain databases. DBPATH can also specify a list of directories (in addition to the current directory) in which DB–Access looks for command scripts (.sql files).

DBUPSPACE

The DBUPSPACE environment variable lets you specify and constrain the amount of system disk space that the UPDATE STATISTICS statement can use when trying to simultaneously construct multiple column distributions.

Example: To set DBUPSPACE to 2,500 kilobytes of disk space and 1,000 kilobytes of memory

export DBUPSPACE 2500:1

DBSPACETEMP

The DBSPACETEMP environment variable specifies the dbspaces in which temporary tables are built.

Example: The following command to set the DBSPACETEMP environment variable specifies three dbspaces for temporary tables.

DBSPACETEMP=sorttmp1:sorttmp2:sorttmp3

After you set this value, the database server can use no more than 2,500 kilobytes of disk space during the execution of an UPDATE STATISTICS statement. If a table requires 5 megabytes of disk space for sorting, then UPDATE STATISTICS accomplishes the task in two passes; the distributions for one half of the columns are constructed with each pass.

INFORMIXSERVER

The INFORMIXSERVER environment variable specifies the default database server to which an explicit or implicit connection is made by an SQL API client, the DB–Access utility, or other IBM Informix products. This must be set before you can use IBM Informix client products.

SQLHOSTS

The INFORMIXSQLHOSTS environment variable specifies where the SQL client or the database server can find connectivity information.

PDQPRIORITY

For Dynamic Server, 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.

For Extended Parallel Server, the PDQPRIORITY environment variable determines only the allocation of memory resources.

export PDQPRIORITY=HIGH|LOW|OFF|resources

  • resources: Is an integer in the range 0 to 100. Value 1 is the same as LOW. Value 0 is the same as OFF (for Dynamic Server only).
  • HIGH: When the database server allocates resources among all users, it gives as many resources as possible to the query.
  • LOW: Data values are fetched from fragmented tables in parallel.
  • OFF: PDQ processing is turned off (for Dynamic Server 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.

An application can override the setting of this environment variable when it issues the SQL statement SET PDQPRIORITY

PSORT_NPROCS

The PSORT_NPROCS environment variable enables the database server to improve the performance of the parallel-process sorting package by allocating more threads for sorting.

Example: The following command sets PSORT_NPROCS to 4

export PSORT_NPROCS=4
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