In general, the primary and secondary system logs should not be offloaded because you need high performance access. So if you have enough storage in the coupling facility for the system logger log streams, you do not need to spend much time estimating the capacity needed for DASD log data sets.

In contrast, you should estimate the capacity for DASD log data sets needed by forward recovery log streams and the RRS archive log stream because you will keep the log information until you think it is no longer needed to perform a forward recovery, probably because you have taken one or more backup copies. When you decide that you no longer need the forward recovery log entries, you need to archive or delete them yourself.

For example, if you take a backup copy of your VSAM data sets once a week, you might choose to delete the forward recovery log stream in DASD log data sets one week after taking the backup. In this case, you would estimate the capacity needed by the DASD log data sets for your redo logs for one week.