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Reading multiple log files concurrently

NGT Recover can reduce recovery elapsed time by using multiple log readers with the MAXLOGS option.

Rules for using the MAXLOGS option to indicate the number of log readers are as follows:

  • Memory usage

    Memory usage will increase by approximately 1.8 MB for each concurrent log reader execution to a maximum of 20MB. For example, if a job has specified MAXLOGS 4, an additional 7.2 MB of storage will be required during the LOG INPUT phase in an NGT Recover job.

  • Setting MAXLOGS and MAXDRIVES

    Use the following algorithm to calculate a first try at values for MAXLOGS and MAXDRIVES if you have archive logs on tape (not including logs migrated to tape with DFHSM):

    1. Divide the number of tape drives that you have available for recoveries by the number of concurrent NGT Recover jobs that you plan to run. This number is your value for MAXDRIVES. Do not reduce MAXDRIVES below the maximum number of image copy and change accumulation tapes (input and output) for one object.

    2. Add the higher of 4 or the number of DASD log files that you anticipate reading to MAXDRIVES to calculate your value for MAXLOGS.

    If all your log files are on DASD or are migrated by using DFHSM or a similar product, use values of 0 (zero) for MAXDRIVES and 6 for MAXLOGS. MAXDRIVES 0 leaves the number of tape drives unconstrained.

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