JCL Generation data sets sizing function
You can use the JCL Generation data set sizing function to tailor the data set sizes when the JCL is built.
The function gathers information from one of the following sources (shown in general order of accuracy, from most accurate to least accurate):
- The BMC Statistics repository (statistics that the BMCSTATS or BMC AMI Stats utility gathers)
- Db2 system catalog (statistics that the IBM RUNSTATS utility gathers)
- Results of VSAM object sampling
- Default data set allocation parameters that are set from the JCL Generation Individual Data Set Options panel
Whether using the BMC Statistics repository, object sampling, or no sizing, JCL Generation obtains some information from the Db2 system catalog.
The formulas for estimating data set size are taken from the documentation for the IBM Db2 utilities and from the documentation for the BMC utilities. The following table shows the statistics that JCL Generation uses for space estimation and the source of the statistics:
Data set sizing values and sources
Source | |||
|---|---|---|---|
Value | BMCSTATS | IBM RUNSTATS | VSAM sampling |
Number of active pages | X | X | X |
Number of modified pages | X | NA | X |
Page size | NA | X | NA |
Maximum row length | NA | X | NA |
Average row length | X | NA | X |
Number of rows | X | X | X |
Number of non-clustering indexes | NA | X | NA |
Longest key | X | X | NA |
Number of foreign keys | NA | X | NA |
Number of indexes | X | X | NA |
Longest foreign key | NA | X | NA |