Saving access path information for static SQL statements
You can use package copies to automatically save pertinent catalog table and directory records for static SQL statements when you bind a package or rebind an existing package.
About this task
When a performance regression
occurs after you rebind a package, you can use the saved historical
information to switch back to the older copy of the package and regain
the old access paths. You can also use the historical information
in conjunction with the APREUSE bind option to specify that Db2 tries
to reuse the existing active access paths for static SQL statements
when you rebind packages.Procedure
To save access path information for static SQL statements:
- EXTENDED
-
Db2 saves the active copy, and two older copies, which are known as the previous and original copies. Db2 replaces the previous copy with the former active copy and saves the newest copy as the active copy. Db2 saves the original copy at the first rebind that EXTENDED is specified and retains the original copy unchanged at subsequent rebinds.
Multiple phased-out copies can also be saved for phase-in of package rebinds. For more information, see Phase-in of package rebinds.
EXTENDED is the default value.
- BASIC
- Db2 saves the active copy and one older copy, which is known as the previous copy. Db2 replaces the previous copy path with the former active copy and saves the newest copy the active copy.
- OFF
- No copies are saved.
When you rebind a package with the PLANMGMT (EXTENDED) or (BASIC) options, the following options must remain the same for package copies to remain usable:
- OWNER
- QUALIFIER
- ENABLE
- DISABLE
- PATH
- PATHDEFAULT
- IMMEDWRITE
