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Identify holder of a resource (ENQHOLD) z/OS MVS Programming: Authorized Assembler Services Reference SET-WTO SA23-1375-00 |
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Use the ENQHOLD SYSEVENT to identify a holder of a resource causing contention. SRM may boost the service to the resource holder to help resolve the contention more quickly. A holder can be either an address space or an enclave. You must specify the address space or enclave in the parameter list pointed to by register 1. Use the IRAEVPL mapping macro described in z/OS MVS Data Areas in z/OS Internet Library at http://www.ibm.com/systems/z/os/zos/bkserv/. Specify either the ASID or STOKEN value for the address space or the enclave token for the enclave. The enclave token must have been obtained from the IWMECREA macro or IWMESQRY macro. Specify parameter TYPE=3 for SYSEVENT ENQHOLD and ENQRLSE to pass the following data to SRM:
When using enclaves for tasks that serialize on resources using
the ENQ macro or the latch manager callable services, note that a
task cannot change its transaction status. That is, it cannot join
or leave an enclave, while holding a resource using ENQ or the latch
manager. Otherwise, enqueue promotion processing might not work properly.
The recommended sequence is:
In addition, to ensure correct enqueue promotion processing, a
task executing in an enclave should not make the following types of
ENQ requests:
Input register informationIf this SYSEVENT is invoked with the TYPE=3 keyword, then register 1 must point to a parameter list. The parameter list must be non-pageable and addressable via the caller's primary address space. To map the parameter list, use the IRAEVPL mapping macro described in z/OS MVS Data Areas in z/OS Internet Library at http://www.ibm.com/systems/z/os/zos/bkserv/. Return and reason codesWhen processing is complete for the ENQHOLD SYSEVENT, the last byte of register 15 contains one of the following hexadecimal return codes:
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