Joined: 23 Nov 2006 Posts: 19270 Location: Inside the Matrix
"REXX" datasets (if i understand your question) are no different than other partioned datasets.
The % used is calculated by taking the amount of space used and dividing by the total space. Using that answer (a percent), you can subtract from 100 and see the % of space used and the free space %.
Keep in mind that a pds may be "full" with only one member. This is because space is not dynamically reclaimed when an updated version of a member is saved. Compressing the library will "free" the unused space.
Cylindars may calculated by dividing the number of tracks by 15. Keep in mind that different device types have different capacities, so the "same" space allocation will allocate different amounts of physical space - check with your storage management people for which device types your location uses. I'd suggest you look at this prior topic:
If i misunderstood your question, please ask for more.