Altering an online HALDB database when ACB libraries are used

Altering the structure of an online HALDB database in an IMS system that uses an ACB library requires coding the changes to the database and program view definitions in utility macro instructions, performing DBD and ACB generations, issuing the INIT OLREORG OPTION(ALTER) command, and performing the Online Change (OLC) procedure.

The HALDB alter function uses dynamic allocation to allocate the staging ACB library. If dynamic allocation of the staging ACB library is not already enabled, you can enable it by using the DFSMDA macro and the IMSDALOC procedure to build the dynamic allocation member named IMSACB.

The high-level steps required to apply database changes with the ALTER option include:

Procedure

  1. Code the changes to the database structure in the SEGM and, if necessary, the FIELD input statements of the Database Generation (DBDGEN) utility.
  2. Generate the DBD members by running the DBDGEN utility with the changed macros.
  3. Generate the PSB members for the application programs that access the database.
    If database versioning is enabled, you are not required to update the PSBs of the application programs that access only prior versions of the database.
  4. Generate the ACB members into the ACB staging library by using one of the following methods:
    • If the IMS catalog is enabled in your system, run the ACB Generation and Catalog Populate utility (DFS3UACB) to generate the ACB members and populate the IMS catalog in a single job step.
    • If the IMS catalog is not enabled in your system, run the ACB Maintenance utility.
  5. If necessary, set the ALTERSZE values in the RECON data set to alter the OSAM block or VSAM CI sizes of the output data sets.
  6. Issue the IMS type-2 INITIATE OLREORG OPTION(ALTER) command to apply the changes to the online database.
    After the command is issued, application programs that use the old database structure can continue to access the database until online change is performed.
  7. Enable access to the new database structure by using the member online change procedure.
    A HALDB online alter operation is not complete until the ACB members for the altered database that are in the staging library are activated.