Configuration Best Practices › Checkpoint Data Set Configuration

Checkpoint Data Set Configuration

Allocate enough space to allow the checkpoint data set to accommodate significant growth and assign the checkpoint data set to a low-impact volume that is separate from the spool data sets.

Business Value:

Having a large checkpoint data set on a low-impact volume will prevent the considerable operational issues involved in resizing a full checkpoint file and moving it to different volumes.

Additional Considerations:

CA Spool needs one checkpoint data set and one or more spool data sets. The checkpoint data set and spool data sets must be permanently allocated as part of the installation process.

Optionally, a secondary checkpoint data set may be defined, which will then be used as a duplex copy of the primary checkpoint data set. This data set is used for manual recovery in case the primary checkpoint data set becomes unusable.

Note: In general, we do not recommend that you use a duplex checkpoint data set as it causes the checkpoint elapse times to double and because physical disk crashes are extremely unlikely.

The checkpoint data set must be allocated in cylinders, and in one extent. CA Spool uses only the first extent of the data set for checkpoint, and any additional extensions are ignored.

The checkpoint data set size requirement is mostly dependent on:

• The NUMFQES (number of file queue elements) parameter

  Note that NUMFQES is really dependent on the length of time that files are kept before purging and the number of files created during that time cycle.

• The size of the spool data set configuration. 

For example: If you keep files for two days and you create 50K files per day, a minimum value of NUMFQES=150000 is suggested to allow for growth and temporary workload increases.

Because spool data sets might be added "on the fly" using the REINIT command, we recommend that you allocate some extra checkpoint data set space to allow the spool data set configuration to grow.

More Information:

See the topic Checkpoint Data Set Size Calculation section in the "Storage Estimates" appendix in the CA Spool Customization Guide for the formula to use when calculating the size of the checkpoint data set.