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ISGNQXITFAST — Fast ISGENQ / ENQ / DEQ Installation Exit z/OS MVS Installation Exits SA23-1381-00 |
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ISGNXITFAST is the IBM® recommended replacement for ISGNQXIT and should be used except where restrictions apply. For each ENQ/DEQ/RESERVE request with SCOPE=SYSTEM or SCOPE=SYSTEMS, the system invokes the Fast ENQ/DEQ Installation Exit, ISGNQXITFAST. The exit routine can modify attributes of the request prior to Resource Name List (RNL) processing. See z/OS MVS Planning: Global Resource Serialization for the installation flow through ENQ/DEQ exits. By altering
the ISGNXITFAST exit parameter list, the exit can:
Note: The exit routine cannot change the scope
nor UCB address of a request when the program issues the ENQ or ISGENQ
macro with RNL=NO. The Nqxp_SF1_RnlEqNo bit passed in the parameter
list indicates if RNL=NO was specified.
This exit is
invoked under the caller's unit of work on the system
where the caller is running. For global resource requests, the exit
is invoked only on the system where the request is made.
Note:
Replacing the Exit RoutineUnlike RNL changes, GRS does not know how an exit alters the resource identity of a request. Therefore, to maintain data integrity, do not make an exit change that alters the resource identity of any outstanding or in-flight ENQ or DEQ requests. The resource identity consists of the QNAME, RNAME, SCOPE, and hardware reserve status. When you make exit changes, first stop the programs that are currently using the resource, and do not resume the programs until all the exit changes in the GRS complex have completed. For information regarding dynamic exit routine replacement, see Replacing a Dynamic Exit Routine. Exit Routine EnvironmentISGNQXITFAST
receives control in the following environment:
Exit Recovery is as follows.
Exit Routine ProcessingThe ISGNQXITFAST exit routine is invoked for every ISGENQ/ENQ/DEQ/RESERVE request issued for a resource. If any exit routines are defined to the dynamic exits facility, those routines are invoked before Resource Names List processing. If any ISGNQXIT exit routines are defined, these are run after the ISNGQXITFAST exit routines are run. By
updating and using information in the parameter list, the exit routine
alters the following characteristics of the request:
The exit routine can also indicate that RNL processing can be bypassed. Programming ConsiderationsObserve
the following conventions when coding a Fast ISGENQ/ENQ/DEQ exit routine:
Entry SpecificationsThe system passes a NQXP parameter list to the exit routine. Registers at Entry: The contents of the registers on entry to the exit are as follows.
Parameter List Contents: Register 1 contains the address of the exit parameter (NQXP) that is mapped by macro ISGYNQXP. Refer to z/OS MVS Data Areas in z/OS Internet Library at http://www.ibm.com/systems/z/os/zos/bkserv/ for the mapping of the ISGYNQXP data area. Return SpecificationsThe ISGNQXITFAST installation exit sets the appropriate request flag and alters the value in the parameter list. For example, to change the major name, the exit sets Nqxp_RFI_ChangeQName to B'1' and Nqxp_CP_QNAME to the new major name. Registers at Exit: Upon return from the exit processing, the register contents must be as follows.
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Copyright IBM Corporation 1990, 2014
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