Making online changes

IMS provides several different options for making changes to resources in an online IMS system.

The options for making changes to resources in an online IMS system include:
  • When Dynamic resource definition is enabled, the IMS type-2 commands CREATE, UPDATE, and DELETE. The IMPORT command can also be used to activate resources from definitions that are stored in either the IMSRSC repository or a resource definition data set (RDDS).
  • When the IMS management of ACBs is enabled, the IMPORT command to activate DBD and PSB resources from new or modified definitions that were previously stored in the IMS catalog by using DDL or one of the IMS catalog population utilities.
  • The database alter functions
  • The online change function

IMPORT command for DBD and PSB changes

When the IMS management of ACBs is enabled, database definitions (DBDs) and program view definitions (PSBs) in the IMS catalog can be activated in an online IMS systems by issuing the IMPORT DEFN SOURCE(CATALOG) command. The DBDs and PSBs must be submitted to the IMS catalog by using either DDL or one of the population utilities with the MANAGEDACBS control statement specified.

Dynamic resource definition (DRD)

DRD enables you to make online changes to certain runtime resource definitions without using the online change process. To change other resources online (for example, resources in IMS.ACBLIB), you still need to use the online change process. With DRD, you can issue type-2 commands to create, update, and delete the runtime resource definitions dynamically, or use the enhanced Destination Creation exit routine (DFSINSX0), formerly called the Output Creation exit routine, to create transactions (and, if necessary, the programs that are associated with the transactions) instead of using the online change process.

You must ensure that:

  • Commands are routed to and executed on the systems where you want the changes to be applied
  • Any changes made dynamically with the DRD commands are recovered across a cold start
  • The resource and descriptor definitions are exported to an RDDS

DRD enables you to create, update, query, and delete the following IMS resource definitions and their descriptor definitions dynamically, without using the system definition or online change processes:

  • Application programs
  • Databases
  • Fast Path routing codes
  • Transactions

Because DRD uses type-2 commands, you can only use DRD where your IMS is configured as follows:

  • A single-IMS IMSplex that is configured with a minimal Common Service Layer that include an Operations Manager (OM) and a Structured Call Interface (SCI), but no Resource Manager (RM). This configuration is also known as an enhanced command environment.
  • A multiple-IMS IMSplex that is configured with a full CSL (OM, SCI, and RM).

Database alter functions

The online alter function for DEDB databases is different than the online alter function for HALDB databases.

You modify online DEDB databases and areas by using the DEDB Alter utility.

You modify online HALDB databases and partitions by using the ALTER option of the INITIATE OLREORG command.

Only certain types of changes can be made to a database by using the alter function. The types of changes you can make differ depending on whether you are modifying a DEDB or HALDB database.

Online change function

There are two variations of the online change function:
Local online change
Allows you to make online changes to IMS resources for one IMS.
Global online change
Allows you to coordinate online changes to IMS resources across all IMS systems in an IMSplex.

The subtopics in this section describe the IMS online change function with DRD disabled.