IBM Mainframe Forum

Hi,

Is there any ISPF command/utility exists where I can find out how much space(TRK/CYL) is required to a dataset for 'N' number of records.?


thank you

No. I believe there are Rexx execs floating around that can compute this for you, though you would have to provide LRECL and BLKSIZE in addition to number of records. No, I do not have one.

thanks for the response steve.. i beleive there a tool exists which can count how many records can fit in a dataset.. any idea if there any ISPF option..

There is an IBM quick reference which will give you what you want - cannot remember its refernce number and do not have time to look for it. Also, as Steve has said - there are things floating about "out there". You probably did not Google. Best to create your own - if there is not already an in-house version.

And if by ISPF option you mean is there one that can be accessed via the ISPF menus then why do you not search the b******y menus yourself or read the ISPF tutorial/documentation. Remember that menus can be tailored in-house so that some 'tools' appearing on the menus are in-house.

i have searched all that.. googled thru and finally came to u guys.. never mind i ll see thank you

The amount of space required depends not only on the number of records, but also the length of each record and how many records are in each block (since the block is what is written to disk). You need to Google GX26-4577 to find the 3390 reference manual that tells you how many records will fit in a track for the various block sizes. When using 80 byte records, for example, the best block size allows 698 records per track while the worst block size allows 156 records per track. So merely by changing the block size, a data set can use over 4 times the number of tracks for the same number of records.

You could use a SORT in copy mode to count the records; there are other ways (and vendor tools such as File Aid can provice record counts as well).

see here for a blocks per track calculator,
after You have found the number of records that fit on a track for a certain blocksize
a simple division will tell how much space allocate
http://ibmmainframes.com/about55037.html

You may also choose to allocate in records. Google on AVGREC for more information and examples of this. Over 20 years ago IBM began recommending this approach to allocation which requires SMS.

The advantage is that all you need to know is the average length of records you are allocating and the approximate number of records.