Space calculator - Number of records reqd

chaitanya.sameer · New User Joined: 13 Mar 2007 Posts: 2 Location: USA

Hi -

Can anybody provide me an idea about how to calculate the number of records per dataset provided the properties of a dataset. Do we have any tool as such to do the same?

For example we have a GDG with the following attributes:
//DOCM DD DSN=xxxx.xx.xx..xxxx(+1),
// DISP=(NEW,CATLG,DELETE),
// SPACE=(15000,(30,6),RLSE),
// AVGREC=K,
// DCB=(CU.GDG,
// LRECL=15000,
// RECFM=FB)

The disk model is 3390. I want to get the maximum number of records that could be inserted in this GDG. Your help on this is appreciated.

Thanks in advance..!

dick scherrer · Posted: Tue Mar 13, 2007 8:01 am

Hello,

You best information source is to talk with your storage management people. The definition you've provided will not store many records.

Your jcl says to allocate space in blocks of 15000 bytes and that lrecl is 15000. If your lrecl and blocksize are the same you have asked for primary space for 30 records with some number of secondaries (6 at a time). How many secondaries you may allocate depends on your environment. Again, this information should be easily gotten from the storage management people.

It is more typical to estimate space on the basis of lrecl * # of records.

chaitanya.sameer · New User Joined: 13 Mar 2007 Posts: 2 Location: USA

Since the block size and the LRECL are the same; Primary space of 30 and AVGREC=K implies the number of records to be 30K in this dataset. Apart from this (i.e. after the 30K records) I believe the secondary extents come into picture.

Please correct me if I am wrong.

dick scherrer · Posted: Tue Mar 13, 2007 8:33 am

Hello,

Sorry 'bout that - missed that parameter

Yes, after the primary, the secodary allocation comes into the picture.

Depending on your site, the number of possible secondaries may vary. Also, when a secondary is allocated, it may or may not be the full size.

As i posted earlier, it is more typical to calculate space based on file size rather than pick some allocation definition and then try to figure how many records it will hold.