Activating database changes by using the online change function

In IMS systems that use DBD, PSB and ACB libraries, you can use the online change function to apply database changes, including changes to full-function databases, full-function HALDB master databases, and Fast Path DEDB databases, to online IMS systems without stopping them.

Note: The online change function is not supported and the online change commands are rejected when the IMS management of ACBs is enabled.

In IMS systems that manage ACBs, database changes are made in the online IMS system by submitting the changes to the IMS catalog. Changes are submitted to the IMS catalog by using SQL DDL statements or by one of the population utilities for the IMS catalog. Some changes that are submitted by DDL are activated in the online system automatically. All other changes are activated by issuing the IMPORT DEFN SOURCE(CATALOG) command.

MSDBs do not support the online change function.

The online change function for DEDBs allows both database-level and area-level changes. A database-level change affects the structure of the DEDB and includes such changes as adding or deleting an area, adding a segment type, or changing the randomizing routines. An area-level change involves increasing or decreasing the size of an area (IOVF, DOVF, CI). An area-level change requires the user to stop only that area with the /DBRECOVERY command; a database-level change requires the user to stop all areas of the DEDB.

Unlike standard randomizers that distribute database records across the entire DEDB, two-stage randomizers distribute database records within an area. By using a two-stage randomizer, changes to an individual area's root addressable allocation are area-level changes, and only the areas that are affected need to be stopped.

To use online change with full-function databases, HALDB master databases, and DEDB databases, perform the following steps:

Procedure

  1. Allocate the data sets for online change as described in IMS Version 15.3 Installation.
  2. Run a MODBLKS system definition if additions, changes, or deletions to the system definition DATABASE (and possibly APPLCTN) statements need to be made (see IMS Version 15.3 System Administration for more information).
  3. Run the necessary DBDGEN, PSBGEN, and ACBGEN (see IMS Version 15.3 System Utilities).
    Note: All changes to ACBLIB members that resulted from the ACBGEN execution are available to the online system after the online change (provided that the changed PSB and DBD resources are defined in the online system).
  4. Update the security definitions of the IMS system's security facilities to include any new databases. Security facilities can include RACF®, another external security product, and exit routines. For more information on IMS security, see IMS Version 15.3 System Administration.
  5. Allocate the database data sets for databases to be added.
  6. Load your database.
  7. For Fast Path, online change must be completed before the database can be loaded. Also, Fast Path can only load databases online; batch jobs cannot be used.
  8. If dynamic allocation is used in a z/OS® environment, run the dynamic allocation utility.
  9. Use the Online Change Copy utility (DFSUOCU0) to copy your updated staging libraries to the inactive libraries (see IMS Version 15.3 System Utilities for information on running this utility).
  10. Issue the operator commands to cause your inactive libraries to become your active libraries (see IMS Version 15.3 Operations and Automation for the commands that are used for online change).

If a database in a z/OS environment needs to be reorganized because of changes to the active ACBLIB data set, /DBR must be issued to deallocate the database before the /MODIFY COMMIT command that introduces the ACBGEN changes. The commands /DBR, /DBD, or /STA DATABASE ACCESS= must be completed to take the areas of the database to be changed or deleted offline before issuing the /MODIFY COMMIT command.