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kalidasv · Beginner Joined: 05 Mar 2009 Posts: 13 Topics: 8

For fixed block files, the block size is normally a multiple of the record size.

What is the norm when it comes to variable length files? Say my record size is 40 to 50 bytes.

BLOCK CONTAINS ___ TO ___ CHARACTERS
RECORD CONTAINS 40 5O 50 CHARACTERS

kolusu · Posted: Sat Apr 18, 2009 12:30 pm Post subject:

kalidasv,

When RECFM=VB, the value of the LRECL= option is the length of the longest record plus 4 bytes that hold record descriptor information. The value of the BLKSIZE= option can be any value up to 32,760, as long as it is at least 4 bytes longer than the value of the LRECL= option. (These 4 bytes are the block descriptor information.)

Kolusu

Bill Dennis · Posted: Mon Apr 20, 2009 8:20 am Post subject:

Because the blocksize can vary, it's usually chosen to complement the storage medium.

DASD - Half-track blocking is usually most space efficient.
TAPE - The largest block possible makes the best use of tape channels and media characteristics such as inter-block gaps.

If you specify BLKSIZE=0 in the JCL, the system determines the best value based on the device to which you're writing.
_________________
Regards,
Bill Dennis

Disclaimer: My comments on this foorum are my own and do not represent the opinions or suggestions of any other person or business entity.

kalidasv · Beginner Joined: 05 Mar 2009 Posts: 13 Topics: 8

Thanks Kolusu and Bill.