Pointer validation

The analysis function validates the logical integrity of pointers to the root and direct dependent segments. You can specify an implicit value for the POINTER_VALIDATION keyword in the GLOBAL command. This keyword value is used by all analysis functions within the job step. To override the GLOBAL command value, specify the POINTER_VALIDATION keyword explicitly on the ANALYZE command.

  • POINTER_VALIDATION=FULL constructs a complete cross-reference of every pointer and segment occurrence. When you specify POINTER_VALIDATION=FULL, the analysis process performs the following tasks:
    • Checks every pointer to ensure that a segment of the proper type actually appears at the referenced relative byte address (RBA)
    • Checks that every segment is referenced by one and only one physical child first (PCF) or physical twin forward (PTF) pointer
    • Identifies the complete chain of dependent segment occurrences associated with their parent segment (the PCF/PTF pointers)
    • Checks physical child last (PCL) and subset (SSPTR) pointers to verify that the segments which are referenced appear in the chain that is defined by the PCF/PTF pointers
    • Checks all keyed segments for correct key sequencing to ensure that the sequence keys of logically adjacent segments are ascending and unique

Note

Because many statistics that are required for report generation can be collected only when POINTER_VALIDATION=FULL, certain reports are not produced if other values are selected. The following reports will not be generated if POINTER_VALIDATION=QUICK or POINTER_VALIDATION=OFF is selected:

  • Segment I/O Analysis Report
  • Record Length Analysis Report
  • Record Placement Analysis Report
  • POINTER_VALIDATION=QUICK (the default) generates a checksum for each segment type within each unit of work (UOW). The checksum consists of the sum of the RBAs for each segment occurrence minus the RBAs of all PCF/PTF pointers to the segment type. Because there should be exactly one PCF/PTF pointer to each segment, a non-zero value indicates a pointer problem. A second checksum consists of the sum of the RBAs for each segment with a null PTF pointer minus the RBAs of all PCL pointers to the segment type. A non-zero value indicates a problem. SSPTR pointers are not validated in this mode.
  • POINTER_VALIDATION=OFF bypasses logical integrity verification of pointers to the root and direct dependent segments. The analysis function still reads the area to perform physical validation and to gather statistics.
  • POINTER_VALIDATION=NONE specifies that the analysis function is not to be executed. This value is valid only on GLOBAL, REORGANIZE, RELOAD, CHANGE, and IMAGECOPY commands; it is not valid when used with the ANALYZE command. This value is used to completely cancel the analysis process as an override of the POINTER_VALIDATION=QUICK default, which otherwise occurs during these processes.

Related topic

Verifying-area-integrity


 

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