ACB library and HALDB alter

If you use ACB libraries, before you start an alter operation you must generate the ACB members that define the new structure of the database into the staging ACB library. If you enable the IMS management of ACBs, you do not need to use staging and active ACB libraries to alter the structure of a HALDB database.

If you have not enabled the IMS management of ACBs and you use ACB libraries, the ACB members must be maintained in the staging library until the online change function clears the ALTER IN PROGRESS status from the database partition records in the RECON data set.

The staging ACB library must be available to all IMS systems that share the database and any batch application programs or utilities that access the database. You can use a single, shared staging ACB library or multiple staging ACB libraries with cloned copies of the ACB members that contain the database changes. You must enable dynamic allocation and deallocation of the staging ACB library by defining TYPE=IMSACB DFSMDA macros.

If the ACB members for the altered database are modified or deleted from the staging library while the partition records have an ALTER IN PROGRESS status, application programs and utilities cannot access the database and the online change function cannot activate the new database structure. If the ACB members are modified or deleted, you can restore access to the database and complete online change by restoring the staging ACB library to its state at the time that alter processing began.

After all of the partition data sets are altered, the ACB members in the staging library must be added to the active ACB library to enable access to the new database structure.

To add the ACB members to the active ACB library, use the ACB member online change function. The member online change function copies from the staging ACB library to the active ACB library only the ACB members of the altered database.

If necessary, you can use either the local online change function or the global online change function. However, both of these methods require you to copy the ACB members from the staging library to the inactive ACB library before you start the online change process. These methods also replace the entire ACB library instead of only the altered ACB members.

Unless database versioning is enabled to allow certain application programs to continue accessing the database without modifications, you must also activate application programs that reference the altered segments in the database when you activate the new ACB members.

After the ACB members are activated, the staging library is no longer required.