Relationship of frequency and maximum number of backup versions

Proper use of the FREQUENCY and NUMBER OF BACKUP VERSIONS (DATA SET EXISTS) attributes can give added assurance that data sets can be recovered. Assume that you specify a frequency of one day and a maximum number of versions of three. If the data set changes daily, the user has only two days to detect any errors that occur in the data set before the oldest backup version contains the error. If the error is not detected in two days, the user cannot use a backup version to recover the data set.

Now assume that you specify a frequency of two days and a maximum number of versions of three. If the data set changes daily, the user has six days to detect the error before the last backup version contains the error. However, each successive backup version will contain two days’ worth of daily changes, and this may not provide enough granularity for your needs.

You can also control the number of days that a user has in which to detect errors by increasing the number of backup versions retained.