Using the SET Command to Quiesce Work

To use this method of stopping APPC work, issue the SET command to specify an APPCPMxx parmlib member that contains one LUDEL statement for each LU to be deleted. For example, if you wanted to delete an LU named MYLU, you would first code a parmlib member such as APPCPM1D in the following example.

Figure 1. APPCPM1D

LUDEL
  ACBNAME(MYLU)

After coding the parmlib member, issue the following SET command.

SET APPC=1D

After you activate the parmlib member through the SET command, APPC/MVS:

Rejects any new conversations (that is, inbound or outbound Allocate requests) to or from the LU specified in the LUDEL statement.
Allows each existing conversation to continue without interruption. Existing conversations are those for which — at the very least — one LU has successfully sent and its partner LU has successfully received the Allocate request.
Issues message ATB051I to hardcopy, to indicate that the LU has been deleted from the configuration.
Deletes the LU's association with a VTAM® generic resource name, if any.
Closes the ACB for the LU, as soon as existing conversations have ended. If the LU handles protected conversations, APPC/MVS defers resynchronization processing for incomplete units of recovery, if any.

By adding the PERSIST keyword on the LUDEL statement for a LU, APPC/MVS will not deactivate any persistent sessions between the LU and its partners. This will allow you to add this LU back into the configuration later, yet not lose any of the sessions that were active at the time of the LUDEL. This assumes that the LU is added back before the persistent sessions time limit expires that was specified on the PSTIMER keyword on the LUADD statement.

At this point, you may restart the LU by issuing a SET command that specifies an LUADD statement for this LU.

Note:

If the PERSIST keyword was specified on the previous LUDEL, you must start the LU with the same NQN capability as the original LUADD for this LU. Failure to do so could cause the LU to not become active and an ATB052E error message with a Reason Code of X'78'.

You may choose to re-add this LU to another image in your sysplex, as long as you have the equivalent VTAM definitions and connectivity, and access to an equivalent TP Profile data set and scheduler.

If you have configured your sysplex to support Multi-Node Persistent Sessions (MNPS), you can add this LU on a different image in the sysplex AND still keep all previous sessions the LU had prior to issuing the LUDEL with the PERSIST keyword.

Because LUDEL processing quiesces work, rather than stopping it immediately, APPC/MVS might not close the ACB for the LU as quickly as you want. To avoid delays, you may eliminate queued work or stop running work before issuing the SET command to process an LUDEL statement. For example, you may stop a class of TPs as described in Stopping a Class of Transaction Programs with the SET Command.

If LUDEL processing has already started, but is proceeding too slowly, you can issue VTAM's VARY TERM command to accelerate the process by terminating one or more sessions for the LU.