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Prime-duplicate DASD Module Comparison (PJ46999)

By Timothy Backus posted Tue September 19, 2023 04:18 PM


When storage devices are mirrored for data redundancy, it is critical that the data in those storage devices be kept in sync. APAR PJ46999 provides a utility to compare the contents of a DASD module with its duplicate module. The prime-duplicate DASD module comparison utility is able to find mismatches in data between a primary DASD module and its duplicate, and writes the mismatches that are found to a file on the z/TPF file system. This utility is useful for scenarios where a DASD module falls out of sync with its duplicate module because you can quickly identify the physical area and file address of the data mismatch. It is up to you to decide how to resolve each mismatch. The utility cannot automatically resolve mismatches.

This utility has the following capabilities:

  • Start a comparison between a DASD module and its duplicate module. The comparison can be run as a normal or low-priority utility.
  • Stop, pause, or restart a single comparison, or all comparisons on a processor.
  • Display settings, details for a single comparison, or an overview of all comparisons across all processors.
  • Set thresholds for the utility, such as the maximum number of concurrent comparisons.

The following example shows a mismatch report. Two mismatches are identified in the record type "    POOL". Both the MCHR and FARF addresses are present for each mismatch that is found:
Started,2023-06-27 15:13:45
00670019000004,00000000181AB6FE,    POOL,00000000001AB6FE,0001,D
006700BB000D37,000000002812C0AE,    POOL,000000000003C0AE,0004,D

For more information about APAR PJ46999, see the APEDIT or see the z/TPF product documentation.