I am confused with so many different ways of calculating space(verified in different forums). And I dont have proper Idea on how to calculate space of a Vsam dataset. I know may be this is a simple question but wan to get more clarity on it. Thats why I have posted here..
RBA is Relative Byte Address. The numbers are pretty raw and difficult to interpret visually. HI-A-RBA is the high allocated RBA. This data set has 36864000 bytes allocated. It gets more difficult when the space is divided into extents.
Used space is very flaky because of CA and CI splits. These inflate the used space. HI-U-RBA will get you started.
I'd suggest you talk to your Storage Admin's or Capacity Planning people, who can probably do this in a matter of minutes using various solutions.
They'll also be aware how the figures should be presented, because HI-A-RBA needs to include indexes and other overheads. It is the physical allocated space that matters as there may be lots of freespace or part used tracks.