How can I determine the space for data set on tape?

saturn · Posted: Wed Aug 20, 2008 11:38 am

How can I determine the space allocated by a given data set on tape? We have to decide if it is useful to store data on tape or on DASD. We already have a lot of data on tape an now we must determine the allocated and used space for these data sets.
For the data on hard disk I can retrieve these information from LISTDSI and LMDLIST. I also tried to use the catalog search module IGGCSI00 but a got only 'FFFFFF' as result for the primary and secondary allocated space.
How can I collect the space consumption on tape without reading the data it self?

Best Regards
Joern Fischer

expat · Posted: Wed Aug 20, 2008 12:07 pm

If you know the lrecl and blocksize and the number of blocks used (usually from your TMS) you can guess-timate it.

Blocks used * INTEGER(blocksize / lrecl) will tell you roughly how many records there are.

Then it's INTEGER(27998 / lrecl) * 2 which gives number of records per 3390 track

So - record estimate / recs per track = tracks required

tracks required / 15 = cylinders required.

saturn · Posted: Fri Aug 22, 2008 12:31 pm

Thanks for the detailed reply! This method is a good idea, but I am not sure if this can help me.
The most of our data sets are variable blocked. From my understanding I can use this rule also for VB’s?
I am not sure but I think our data on tape are compressed. If so, I can’t calculate the space from the block size and record length. Correct?
I have to clarify which TMS we are using and if there is any possibility to call the TMS service via REXX. I have to investigate approximately 300 data sets, this can't be done in a manually process.

expat · Posted: Fri Aug 22, 2008 12:43 pm

Whether the tape data is compressed or not, the result should still be reasonably accurate. Although the data in compressed, the number of blocks used will remain the same.

For VB files, the maximum LRECL will probably give a result which is slightly higher than required, but contingency is never a bad thing

Anuj Dhawan · Posted: Fri Aug 22, 2008 1:53 pm

Hi,

expat · Posted: Fri Aug 22, 2008 2:06 pm

Anuj

Probably a little more accurate, but that does involve reading each tape file, some of which can be rather large.

IMHO the guess-timate method would be much quicker and would not use rather a lot of resource.

From a single listing from the TMS the guess-timate can be calculated for every tape in one pass and use a lot less resource. Especially if you work in a bill per usage site.

saturn · Posted: Sat Aug 23, 2008 2:41 pm

expat · Posted: Sat Aug 23, 2008 3:04 pm

The sort solution will read the tapes.

The TMS reports could probably be produced by yourself via a batch job. The best thing is to talk to your storage team and see what they say. When I have had people come to me and say I need this information, I usually give them the job to run for themselves.