Db2-supplied user tables
You or certain tools might create user tables that are supplied with Db2 on your Db2 for z/OS® subsystem.
Supplied user tables enable you to capture information about data access by using the EXPLAIN function, to monitor query and system performance with monitor profiles, and to limit the use of resources by particular applications or middleware servers by using the resource limit facility. Instances of these tables also enable optimization tools to capture, analyze, and store information about query performance.
Most documentation topics for Db2 12 for z/OS assume that the highest available function level is activated and that your applications are running with the highest available application compatibility level, with the following exceptions:
- The following documentation sections describe the Db2 12 migration process and how to activate new capabilities in function levels:
- FL 501 A label like this one usually marks documentation changed for function level 500 or higher, with a link to the description of the function level that introduces the change in Db2 12. For more information, see How Db2 function levels are documented.
The availability of new function depends on the type of enhancement, the activated function level, and the application compatibility levels of applications. In the initial Db2 12 release, most new capabilities are enabled only after the activation of function level 500 or higher.
- Virtual storage enhancements
- Virtual storage enhancements become available at the activation of the function level that introduces them or higher. Activation of function level 100 introduces all virtual storage enhancements in the initial Db2 12 release. That is, activation of function level 500 introduces no virtual storage enhancements.
- Subsystem parameters
- New subsystem parameter settings are in effect only when the function level that introduced them or a higher function level is activated. Many subsystem parameter changes in the initial Db2 12 release take effect in function level 500. For more information about subsystem parameter changes in Db2 12, see Subsystem parameter changes in Db2 12.
- Optimization enhancements
- Optimization enhancements become available after the activation of the function level that introduces them or higher, and full prepare of the SQL statements. When a full prepare occurs depends on the statement type:
- For static SQL statements, after bind or rebind of the package
- For non-stabilized dynamic SQL statements, immediately, unless the statement is in the dynamic statement cache
- For stabilized dynamic SQL statements, after invalidation, free, or changed application compatibility level
- SQL capabilities
- New SQL capabilities become available after the activation of the function level that introduces them or higher, for applications that run at the equivalent application compatibility level or higher. New SQL capabilities in the initial Db2 12 release become available in function level 500 for applications that run at the equivalent application compatibility level or higher. You can continue to run SQL statements compatibly with lower function levels, or previous Db2 releases, including Db2 11 and DB2® 10. For details, see Application compatibility levels in Db2