Using the VARY Command to Stop Work Immediately

VTAM's VARY TERM and VARY INACT commands allow you to shut down an LU and its work almost immediately. For APPC/MVS LUs, IBM® recommends that you use these commands in sequence:

Issue VARY TERM to terminate all sessions for a specified APPC/MVS LU. When you issue VARY TERM, all TPs involved in existing conversations that are processed through VTAM® receive control.
This interruption prevents TPs from hanging, if they are waiting for an outstanding APPC/MVS or CPI-C call (for example, a TP might be waiting for its partner TP's response to a Confirm call).
Issue VARY INACT without the TYPE parameter to deactivate the specified APPC/MVS LU. When you issue VARY INACT:
- Either VTAM or APPC/MVS rejects new conversations for the LU
- APPC/MVS issues message ATB051I to hardcopy, to indicate that the LU has been deleted from the configuration.
- APPC/MVS immediately closes the ACB for the LU. If the LU handles protected conversations:
  - Units of recovery for those conversations are put into backout-required state;
  - APPC/MVS defers resynchronization processing for incomplete units of recovery, if any; and
  - APPC/MVS unregisters the LU with RRS.
At this point, you may reactivate the LU, so it can begin to process new conversations. Once the LU re-registers with RRS, the LU can resume resynchronization processing for incomplete units of recovery, if any.

If you issue VARY INACT without VARY TERM, or issue VARY INACT with the TYPE operand, work is stopped quickly, but not as cleanly. If any TPs are waiting for an outstanding APPC/MVS or CPI-C call, they might hang indefinitely. For VARY INACT with TYPE=IMMED or TYPE=UNCOND, APPC/MVS cannot return control to such TPs, so you risk more than hanging some work; data loss and resource contention are only some of the possible consequences. Use VARY TERM and VARY INACT in sequence, to make sure you stop work quickly but cleanly.

For VARY command syntax, see z/OS V2R1.0 Communications Server: SNA Operation.