Migrating to Db2 12

Migration is the process of upgrading from Db2 11 to Db2 12.

The Db2 12 migration process uses a single catalog level. For more information about catalog levels in Db2 12, see Function levels and related levels in Db2 12. Before you begin migration to Db2 12, read all information in Preparing your system to install or migrate to Db2 12.

Availability of new function and Db2 12 function levels

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

Activation of function level 100 introduces all optimization enhancements in the initial Db2 12 release. That is, function level 500 introduces no optimization enhancements.

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 12

Function levels in Db2 12

When you initially migrate to Db2 12, Db2 is at function level 100, and you cannot use most new capabilities.

You can use function level 100 to complete migration tasks and verify that the subsystem is stable. In a data sharing environment, you use function level 100 to migrate all members of the group to Db2 12. When the subsystem or data sharing group is stable at function level 100, you can activate a higher function level. After any new function level is activated, fallback to Db2 11 is no longer possible.

Application compatibility in Db2 12

After migration to Db2 12 is complete, you can resolve application incompatibilities and rebind applications at the appropriate application compatibility so that they can use new SQL capabilities. You can do these steps when you are ready and satisfied that your environment is stable on Db2 12. For details see, Application compatibility levels in Db2 12.