how to calculate file size

karthik3883 · New User Joined: 19 Oct 2007 Posts: 37 Location: chennai

Hi,

I need to know how to calculate file size for FB or VB file.could anyone please let me know

Regards
Karthik

Nic Clouston · Posted: Wed Jul 24, 2013 1:13 pm

You will need to do a lot of explaining! File size - number of records? number of bytes? nmumber of blocks? number of tracks? number of cylinders? number of tapes? File can vary in size, record-wise, from zero to millions of records. same sort of thing for the othe other criteria.

expat · Posted: Wed Jul 24, 2013 1:58 pm

And of course for DASD files the size depends on the DASD geometry

Lets start at the beginning, and assume that your are using 3390 geometry.
What is the optimum BLKSIZE for this device type. Google should tell you.

Nic Clouston · Posted: Wed Jul 24, 2013 2:13 pm

Of course, you could always follow the forum rules and search:
a previous topic
And after 3 months in a technical role you should know how to do this - not wait for 6 years. This is a beginner's question. why not join the this sites sister forum for beginners?

Pete Wilson · Posted: Wed Jul 24, 2013 5:21 pm

LRECL x Number of records - is a rough rule of thumb for total bytes.

Another way is to view the file in 3.4 and get the number of tracks used, and assuming you're on 3390 DASD then multiply the number of tracks by 56664 (no of bytes per track). It's not 100% accurate but probably close enough. At least this way it shows what is actually used regardless of the BLKSIZE.

BLKSIZE can have a big effect on file size. If the fle is allocated using System Determined Blksize (SDB) by not specifying BLKSIZE or coding BLKSIZE=0 then it will get the most efficient half track BLKSIZE. But if someone has done something silly like creating a file with RECFM=FB,LRECL=80,BLKSIZE=80 then the file will be multiple time bigger than it needs to be due to most of it being 32 byte interblock gaps.