Initiating a global online change

The INITIATE OLC (initiate online change) command is provided to support global online change, where online change is coordinated across IMS systems in the IMSplex. INITIATE OLC is similar to /MODIFY PREPARE and /MODIFY COMMIT, except that it applies to an IMSplex-wide global online change. OM sends the INITIATE OLC command to one IMS in the IMSplex.

For syntax, environment, and usage information, see IMS Version 15.3 Commands, Volume 1: IMS Commands A-M.

Note: When running in an environment without RM (RMENV=N), this command performs a local online change on the IMS that processes it.

INITIATE OLC prepares for or commits a global online change of IMS resources across an IMSplex.

INITIATE OLC is not supported if local online change is enabled. The INITIATE OLC PHASE(PREPARE) command is rejected if the IMS to which the command is routed does not support global online change. If the INITIATE OLC PHASE(PREPARE) command is rejected and there is an IMS that supports global online change, route the command to an IMS that supports global online change.

The correct online change command sequence is the following:

Procedure

  1. INITIATE OLC PHASE(PREPARE)
  2. /DISPLAY MODIFY
    Use the /DISPLAY MODIFY command to display the work in progress for resources to be changed or deleted, before attempting the COMMIT phase. When COMMIT is successful, the modifications persist across all IMS restarts, unless global online change occurs while an IMS is down.
  3. INITIATE OLC PHASE(COMMIT)

If the INITIATE OLC PHASE(PREPARE) is specified without a FRCABND or FRCCNRML keyword and the command fails because one or more IMS are down or go down before the online change is committed, the online change must be aborted and started over. Issue the TERMINATE OLC command to abort the online change.

If the INITIATE OLC PHASE(PREPARE) is specified with the FRCNRML keyword and the command fails for any IMS, you can proceed with an INITIATE OLC PHASE(COMMIT) command after shutting down those IMS systems where the prepare failed. Otherwise you must abort the online change and start over.

If the INITIATE OLC PHASE(PREPARE) is specified with the FRCABND keyword and the command fails for any IMS, you can proceed with an INITIATE OLC PHASE(COMMIT) command after canceling those IMS systems where the prepare failed. Otherwise, abort the online change and start over.

If the INITIATE OLC PHASE(COMMIT) command fails for any IMS before the OLCSTAT data set is updated, you can either correct the errors and try the commit again or abort the online change with a TERMINATE OLC command.

If the INITIATE OLC PHASE(COMMIT) command fails for any IMS after the OLCSTAT data set has been updated, you can correct the errors and try the commit again. The online change cannot be aborted.

If an IMS abends during online change and the INITIATE OLC PHASE(PREPARE) command was not specified with FRCABND, then issue the TERMINATE OLC command to abort the online change. The INITIATE OLC PHASE(COMMIT) command is not permitted in this case. If an IMS abends during online change and the INITIATE OLC PHASE(PREPARE) command was specified with FRCABND, then the INITIATE OLC PHASE(COMMIT) command is permitted.

Type-1 commands and type-2 commands that come from the OM interface are rejected during the commit phase, if the command changes resources. Commands that change resources could interfere with the online change of the resources. Type-1 commands and type-2 commands that come from the OM interface are permitted during the commit phase, if the command (such as /DISPLAY or QUERY) displays resources. Type-1 commands that are entered from the system console or an IMS terminal are queued during the online change commit phase. These commands run after the online change is committed or aborted.

You can specify INITIATE only through the OM API.

INITIATE is invalid on an XRF alternate and FDR system.

Each IMS participating in the global online change does not issue the same synchronous online change messages to the master terminal or system console that it does for a local online change. The OM command response contains information equivalent to the online change messages that appear for the local online change, such as the DFS3499 message contents.

Each IMS participating in the global online change may issue asynchronous online change messages to the system console, such as DFS3400, DFS3445, and DFS3498. For more information about these messages, see IMS Version 15.3 Messages and Codes, Volume 1: DFS Messages.

The OM command timeout default of 300 seconds (5 minutes) might not be enough time for the online change phase to complete. You might need to specify a timeout value on the command based on the needs of the installation.