Mainframe, MVS and zOS Discussion

Hi,

How to calculate the VSAM file size in GB?

There are different types of VSAM data sets, but in general -- just as with sequential data sets -- you take the average record size and multiply by the number of records. Divide the result by 1024 to get KB, divide again by 1024 to get MB, and divide another time to get GB.

If you have an alternate index, you'll need to compute that separately. And you really should be referencing the IBM Redbook VSAM Demystified which explains almost anything you want to know about VSAM.

Thanks Robert.

There is no way directly in mainframes using which we can find the GB value? And will different VSAM file make a difference?

With mainframes, there are usually several different ways to do something. You could use DCOLLECT, you could approximate the total by going to ISPF 3.4 to find the tracks / cylinders allocated and multiplying by the appropriate value, and so forth.

If the VSAM data set has alternate indexes, they can add up to quite a lot of space by themselves.