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Extensions to the sample program: The sample exit program does not attempt to
control the queue length, or detect poor response for a particular modegroup
differently from the whole connection. This kind of enhancement is something you
might want to add to your own exit program if your applications request specific
modegroups via the allocate command (or via a transaction profile) and you think it
would be useful to control the modegroups individually.
You can also use more complex decisions (such as adding time delays to lessen
the risk of false diagnosis) to decide when to issue the return codes that purge the
queue, and allow queuing to restart.
XISQUE exit for managing IPIC intersystem queues
You can use the XISQUE exit to control the number of queued distributed program
link (DPL) requests for sessions on IP interconnectivity (IPIC) connections.
Note:
v Queued requests for sessions are known as “allocate queues”.
v IPIC connections are also known as “IPCONNs”.
v The equivalent global user exit to control the number of queued requests
for sessions on MRO and APPC connections is XZIQUE: see “XZIQUE
exit for managing MRO and APPC intersystem queues” on page 249.
The XISQUE exit enables you to detect queuing problems (bottlenecks) early. It is
invoked only for DPL requests across IPCONNs.
XISQUE enables allocate requests to be queued or rejected, depending on the
length of the queue. It also allows an IPCONN on which there is a bottleneck to be
terminated and then re-established.
Related concepts
“The session queue management sample exit program, for IPIC connections” on
page 24
When the XISQUE exit is invoked
The XISQUE global user exit is invoked, if it is enabled, at the following times:
v Whenever CICS tries to acquire a session on an IPIC connection to a remote
system and there is no free session available. It is invoked whether or not you
have specified the QUEUELIMIT option on the IPCONN definition, and whether
or not the limit has been exceeded.
Requests for IPIC sessions arise when DPL is used across an IPCONN.
v Whenever an allocate request succeeds in finding a free session, after the queue
on the IPCONN has been purged by a previous invocation of the exit program. In
this case, your exit program can indicate that CICS is to continue processing
normally, resuming queuing when necessary.
Exit XISQUE
When invoked
When:
1. A DPL request for a session on an IPIC connection is about to be
queued
2. An IPIC allocate request succeeds following previous suppression of
queuing.
258 Customization Guide