Adopting new capabilities in Db2 12 continuous delivery
In Db2 12, function levels and application compatibility levels control the adoption of most new capabilities by Db2 subsystems and Db2 applications.
About this task
Function levels are specified by
strings that correspond to the Db2 version,
release, and maintenance value. The format is
VvvRrMmmm, where vv is the version, r is the release, and mmm is the modification level. For example,
V12R1M510 identifies function level 510. For a list of all available function levels in Db2 12, see Db2 12 function levels. Often function
level identifiers are abbreviated. For example,
function level 510
refers to V12R1M510.
- 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
To manage the adoption of new capabilities in Db2 12, use the following overall process:
Apply maintenance to bring the Db2
subsystem to the required code level or higher.
Tip: Apply the maintenance for a code level well before you tailor the catalog level or activate a function level. By doing so, you can verify that Db2 can continue run at the required code level, while you still have the opportunity to identify and remove any problematic maintenance items.Important: Do not attempt to start Db2 at any code level that is lower than the highest ever activated function level, even at the lower star (*) function level. Activate a function level only after you are satisfied that Db2 can continue to run at the required code level.
- If necessary, update the Db2 catalog. You can use a single CATMAINT job that specifies the target function level. If the target function level requires multiple catalog level updates, the CATMAINT job processes each update in sequential order. If a later update in the sequence fails, the previous successful updates do not roll back, and the catalog level remains at the highest level reached. If that occurs, you can correct the reason for the failure and resubmit the same CATMAINT job. Some function levels do not require catalog changes.Db2 12 function levels use the following Db2 catalog levels:
Important: Do not attempt to start Db2 at a lower code level after any part of the CATMAINT job for a higher function level completes. Run the CATMAINT job only after you are satisfied that Db2 can continue to run at the necessary code level. The code to tolerate catalog changes is contained in the code level that delivers the CATMAINT job.
Activate the higher function level.
Some new capabilities and enhancements become available immediately. Optimization enhancements become available after the next full prepare of the SQL statements. The application compatibility level of each application continues to control the use of new SQL capabilities.
When you are ready for applications, and objects such as routines or triggers, to use new SQL
capabilities of the higher function level, rebind or alter them at the higher application
compatibility level. Do this only after you are satisfied that Db2 12 is stable at the higher function level.
You might need to adjust your applications for incompatible changes before they can run at the higher application compatibility level.Tip: Do not raise the default application compatibility level of the Db2 subsystem immediately after migrating or activating a new function level. Instead, wait until applications have been verified to work correctly at the higher function level, and any incompatibilities have been resolved. For details, see Enabling default application compatibility with function level 500 or higher.