DFHZCGRP |
Program initiated by task CGRP to set up the start type
and to call DFHZGRP during initialization. It then analysis the response from
DFHZGRP and decides if CICS® can continue or not. |
DFHZGCA |
Sets the appropriate ZC control blocks to reflect the
currently agreed Change Number Of Session (CNOS) values for an LU6.2 connection. |
DFHZGCC |
Performs catalogue and retrieval of CNOS data.
This
module is called when CICS needs either to store or to recover CNOS values.
During a CICS run, all CNOS values are written to the global catalogue. Under
normal circumstances they are not needed. However, if a persistent sessions
restart is performed, it is necessary to recover the CNOS values which
were in operation at the time of the CICS failure. This is achieved by
having a record on the global catalogue which can be read in during PRSS restart
and used to restore the sessions to their pre-failure state.
This module
will handle the maintenance of the CNOS records during normal CICS operation
and the recovery of the records during PRSS recovery. |
DFHZGCN |
Handles the process of LU6.2 Change Number Of Sessions
(CNOS) negotiation, acting as either the source or target end of the conversation,
and calls DFHZGCA to action the resulting changes. |
DFHZGDA |
The role of DFHZGDA is to take control of APPC conversations
which have persisted across a CICS failure, and to ensure that they are terminated
cleanly, by issuing a Deallocate(Abend) informing the partner LU that the
CICS transaction has abended.
If DFHZGDA is working correctly, the fact
that CICS has failed and been restarted should be transparent to the partner
LU; all he knows is that the CICS transaction to which he was talking has
terminated.
DFHZGDA also performs REJECT_ATTACH processing for synclevel
2 conversation which are started by the partner before Exchange Lognames has
been done after a persistent sessions restart. |
DFHZGPC |
Performs recovery of CNOS values for modegroups.
This
module is called when CICS is performing a persistent sessions (PRSS)
restart. When a PRSS restart is performed, it is necessary to do more than
merely recover the session. It is also necessary to recover the CNOS state
which the sessions had prior to the CICS failure. DFHZGCC will have
maintained a record of the CNOS state on the global catalogue. This record
will now be used in this module in an attempt to restore CNOS values. |
DFHZGPR |
The role of DFHZGPR is to update the global catalog whenever
it is necessary to add, delete, or test for a record indicating that an APPC
connection has a Persistent Resource associated with it.
A Persistent Resource
can be defined as some session state, or piece of work upon which the partner
LU is dependent, and which will be lost in the event of CICS failing. The
only Persistent Resource so far identified is:
Prior to persistent sessions, the failure of the APPC session
tells the partner that these resources have been lost, and drives his recovery.
With the advent of persistent sessions, it is necessary for a persisting CICS
to know that an APPC session had a Persistent Resource associated with it,
so that the connection can be unbound (to drive the partners cleanup) and
then rebound. |
DFHZGRP |
Initialize VTAM® persistent sessions.
DFHZGRP is a
domain subroutine but is called by DFHZCGRP (task CGRP) during initialization.
DFHZGRP is called during ZC initialization or when the VTAM ACB is
opened dynamically by CEMT SET VTAM OPEN or EXEC CICS SET VTAM OPEN by DFHEIQVT.
The module does the following:
- OPNDST RESTOREs or CLSDST/TERMSESS any session that VTAM has held persisting,
depending on start up type and session parameters.
- It calls DFHZGPC to re-instate CNOS records during an EMER restart, or
calls DFHZGCC to delete CNOS catalogue records.
- It initializes the RECEIVE_ANY RPLs and issues the RECEIVE_ANYs.
|
DFHZGSL |
Informs VTAM whether sessions are to persist or not.
This module is called when CICS needs to set, unset or change the Persistent
Sessions PSTIMER value. |
DFHZGUB |
Issue CLSDST or TERMSESS for individual NIBs in a NIBLIST.
This module is called by DFHZGRP to unbind nibs in a niblist in two ways:
- Unbind the entire NIBLIST for COLD, WARM, EMER+XRF and dynamic open.
- Unbind only the NIBs with NIBUSER = 0 for EMER starts.
|
DFHZXPS |
DFHZXPS handles Persistent Sessions recovery for APPC
sessions. It does not deal with non-APPC sessions which are dealt with by
DFHZXRC.
DFHZXPS is called by DFHZACT after OPNDST OPTCD=RESTORE has been
issued successfully for a persisting APPC session. Both single and parallel
APPC sessions are dealt with but there is no difference in the processing.
The task of DFHZXPS is to examine VTAM session tracking data which
was hung off TCTE_PRSS_CV29_PTR by DFHZGRP following a Persistent Sessions
restart and if possible to update the TCTTE to allow work to continue on the
session.
If it is not possible to determine the state of the session
prior to system failure, or the session was not in a state which allows it
to be recovered, the session will be unbound. |
DFHZXRC |
DFHZXRC analyses the Session State Vector data that is
hung off TCTE_PRSS_CV29_PTR by DFHZGRP during an EMER restart, for each persisting
session. The necessary action to cleanup and recover the session is then initiated. |