Using the ENQ/RESERVE/DEQ monitor tool

The main objective of the global resource serialization monitor tool is to assist in planning the RNLs for global resource serialization implementation. The tool monitors ENQ, DEQ, and RESERVE requests, and collects data about the resources and the requesters.
Tip: To collect the same data but with less impact to the ENQ/DEQ path length, instead use SMF 87 subtype 2 records. See Using SMF 87 records for more information.
The objectives of the tool are:
  • Assist in planning the RNLs for global resource serialization implementation.
    • Find the name and the scope of ENQ.
    • Measure the rate and time of the RESERVEs.
  • Reduce DASD contentions and interlock exposures by helping to identify RESERVEs for which changes to RNLs could reduce elapsed time for some jobs and to verify the results of RNL changes that are made.
    • Report RESERVE activities with total and maximum RESERVE time on shared DASD.
    • Report resources that contributed to the RESERVE time.
    • Verify the results when RNLs are implemented.
  • Provide information to assist in the analysis of results of global resource serialization tuning.
    • Measure the global resource serialization ENQ delay for global enqueues, the actual RESMIL value, and the ENQ/DEQ requests rate.
    • Determine ENQ request patterns to help determine who the resource consumers are.
    • Trace global resource serialization ENQ delay using a major name SYSZENQM and a minor name ENQDELAY and minor name with delay value, date and time information (see Figure 1, Figure 2, and ENQ/RESERVE/DEQ restrictions).

An interactive ISPF application allows viewing and printing of the collected data. Alternatively, the data can be written to a sequential data set. Reports can be generated by modifying the sample procedures provided in SYS1.SAMPLIB. If the data is not written to datasets, it is collected in a dataspace associated with the monitor address space. The amount of data saved in the dataspace can be controlled by the DSP PARM (ses Figure 1). The monitor stops collecting data and issues message ISGAU015 - DATA SPACE FULL when the dataspace is full.

Guideline: The monitor's intent is to assist with planning and tuning of RNLs for the implementation of global resource serialization. The monitor uses system resources in order to collect data. IBM® recommends that you do not run the monitor continuously during normal production work. While running the monitor you might observe high CPU in address spaces that issue many ENQ/RESERVE/DEQ requests.

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