Region size requirements for the Reorg function

The Reorg function of FPA operates in a virtual storage region as z/OS® batch job steps. HFPMAIN0 runs in 31-bit addressing mode.

Region size for the Reorg function depends on the size of a UOW, the number of areas being reorganized and of the ITASKCTL specifications used. Typically, database maintenance is a relatively important function. To increase the performance of the Reorg program, it would be advisable to run it in a region that has a relatively high dispatching priority (that is, at least equal to the dispatching priority of a message processing region).

Estimating the region size for Reorg

The region size required for the Reorg function is a function of the size of a UOW, the number of areas being reorganized, and the ITASKCTL specifications.

In most cases, the specification on the EXEC statement for HFPMAIN0 of a region that is too small, is detected during the initialization processing of the main task. This causes processing to be terminated at that point. Under certain conditions, the region size shortfall does not become evident until the actual reorganization has begun. The job must be completely rerun. Thus, the region size calculations must always be performed prior to initiating reorganization processing.

The following worksheet is for estimating the region size that is required for a typical reorganization job. The actual region size depends on the keywords that are specified for the job. Therefore, when you specify the region size in your JCL, use a higher value than the value calculated from this worksheet.

Figure 1. Worksheet for estimating the region size for the Reorg function

FPA programs, internal tables, control blocks         3,020,000

Number of areas defined in DBD * 1,300                ---------

      Internal tables, control blocks              37,500

      Maximum Segment length * 1,000            ---------

      Maximum CISZ * 17                         ---------

                              subtotal          ---------

      Value specified on ITASKCTL * subtotal          ---------

Number of input areas * 7,500                         ---------

Total of CISZ * UOW1 of each area * 4                 ---------

Number of UOWs * 130                                  ---------  (If RFSSCAN=(YES,YES))

Number of UOWs * 70                                   ---------  (If RFSSCAN=(YES,NO) or 
                                                                  RFSSCAN=(NO,YES))

Total bytes of reorganization storage                 ---------

If an analyze step is included in the reorganization process, estimate the region size for the analyze step and use the greater region size. For how to estimate the region size for an analyze step, see Region size requirements for the Analyze function.

If ICACHE=YES is specified, the Reorg function preloads the IOVF part into the data space. The data space size required for the Reorg function is a total of the size of the IOVF part in each area.

The following figure shows a worksheet for estimating the data space size for the Reorg function.

Figure 2. Worksheet for estimating data space size for the Reorg function

Total size of IOVF parts in all areas                  ----------

Total bytes of a data space storage                    ----------