>>-SET ALL_MUTABLES--TO--+-MUTABLE---+------------------------->< '-IMMUTABLE-'
Only Extended Parallel Server supports this statement, which is an extension to the ANSI/ISO standard for SQL.
By default, users can reset the values of some environment variables during a session to support their usage requirements. This capability can sometimes conflict, however, with the resource usage policy set by the DBA. By changing the mutability property of environment variables, a DBA can have more accurate control over resource allocation during a user session.
Settings of the following features frequently have the most impact on resource utilization within a user session, and have the mutability property defined:
Users can reset the mutability of specific features by using the corresponding SET statement. For example, PDQPRIORITY can be made immutable by the SET PDQPRIORITY IMMUTABLE statement. SET DEFAULT TABLE_TYPE MUTABLE can change the default table type. SET ALL_MUTABLES can reset the mutability all of the above features in a single statement.
Typically, the mutability property is set by the DBA in a sysdbopen procedure to control the usage of resources. For a discussion of setting the mutability property in sysdbopen procedure, see IBM Informix Performance Guide.
The DBA can modify all variables, irrespective of their mutability setting. The command
onstat -g mut session_id
displays the current mutability settings for the specified session.
The command
onmode -q
can change the mutability of a specified variable associated with an existing session. See the IBM Informix Administrator's Reference for details of how to use the onstat and onmode utilities.
By default, all environment variables are MUTABLE.
Related statements: SET Default Table Space , SET Default Table Type, SET ENVIRONMENT , and SET PDQPRIORITY
See also the section Setting Environment Variables in SYSTEM Commands, which describes how to use the SYSTEM statement of SPL to change the settings of environment variables for the current user session.