Processing Considerations for Compress

If you try to perform a compress-in-place on a PDSE, IEBCOPY will ignore your request and continue processing with the next control statement.
A compress-in-place does not release extents assigned to the data set.
During a compress operation, you cannot include, exclude, or rename selected members.
You may not change any data set DCB parameters, such as block size, when compressing a data set.