IBM Mainframe Forum

While creating a dataset PDS or PS how do we determine the number of tracks or cylinders to allocate?

Forgot to include how to find Block size?

Number of records = 100000, RECFM=FB, LRECL=125

Blocksize = INTEGER(27998 / LRECL) - Although specifying only RECFM and LRECL will invoke system determined blocksize.

Records per block = Blocksize / LRECL
Records per track = Records per block * 2
Records per cylinder = Records per track * 15

For VB records it is safest to use the maximum LRECL to determine the space requirements, but always use 27998 as blocksize.

The BLKSIZE suggested by expat (27998) is one-half of a 3390 track, the most common device geometry. Smaller blocks waste space due to the physical method of writing the data on the disk.

This link shows the various block sizes and utilizations. http://publibz.boulder.ibm.com/cgi-bin/ ... 1001/B.1.2