Portal | Manuals | References | Downloads | Info | Programs | JCLs | Master the Mainframes
IBM Mainframe Computers Forums Index
 
Register
 
IBM Mainframe Computers Forums Index Mainframe: Search IBM Mainframe Forum: FAQ Memberlist Usergroups Profile Log in to check your private messages Log in
 

 

difference between BLKSIZE and LRECL in terms of PS and PDS?

 
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> JCL & VSAM
View previous topic :: :: View next topic  
Author Message
maridawson

New User


Joined: 24 Jun 2008
Posts: 59
Location: chennai

PostPosted: Thu Jul 17, 2008 8:11 pm    Post subject:
Reply with quote

what is the difference between BLKSIZE and LRECL in terms of PS and PDS?
Back to top
View user's profile Send private message

Terry Heinze

JCL Moderator


Joined: 14 Jul 2008
Posts: 1249
Location: Richfield, MN, USA

PostPosted: Thu Jul 17, 2008 8:20 pm    Post subject:
Reply with quote

Your question is a bit confusing. The members of a PDS have a common LRECL. The members don't have a BLKSIZE, the PDS has one. With a Physical Sequential file, the records have a LRECL and the file itself has a BLKSIZE. All this info is in the JCL Manual.
Back to top
View user's profile Send private message
Robert Sample

Global Moderator


Joined: 06 Jun 2008
Posts: 8057
Location: East Dubuque, Illinois, USA

PostPosted: Thu Jul 17, 2008 10:59 pm    Post subject:
Reply with quote

LRECL is Logical RECord Length -- the length of an individual record (or the maximum size of an individual record for variable length records). BLKSIZE is the physical block size written to the hardware and consists of some number of records (1 minimum, maximum depending on the LRECL and other factors). Physical sequential files and members of a PDS have the LRECL of the file (eg, the record length of each individual record depends on the LRECL of the entire dataset but can vary); BLKSIZE is a characteristic of the entire dataset.

The directory of a PDS has no relationship to the LRECL of the PDS, as each PDS directory block is a 256-byte area.

So to answer your question, BLKSIZE is the physical length of data written to disk or tape and that block contains a number of logical records each no more than LRECL bytes long (and fixed at LRECL bytes long for fixed length files). These definitions apply to PS and PDS files.
Back to top
View user's profile Send private message
Przemyslaw Krekora

New User


Joined: 20 Feb 2008
Posts: 9
Location: Poland

PostPosted: Sat Jul 19, 2008 12:32 am    Post subject: more info
Reply with quote

Continuing, whenever you read data from disk, you read data, block after block. So if for your PDS (for example of course) has blocksize which can have 10 records, there are read always 10 records even when you want to read only one record.
Back to top
View user's profile Send private message
View previous topic :: :: View next topic  
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> JCL & VSAM All times are GMT + 6 Hours
Page 1 of 1

 

Search our Forum:

Similar Topics
Topic Author Forum Replies Posted
No new posts WER247A incompatible lrecl Danielle.Filteau SYNCSORT 8 Tue May 02, 2017 4:04 am
No new posts Changing of LRECL of a file abdulrafi DFSORT/ICETOOL 2 Fri Mar 24, 2017 3:25 pm
No new posts Difference between TWALENG and TWASIZE Arunkumar Chandrasekaran CICS 3 Tue Jan 03, 2017 12:57 pm
No new posts Sticky: difference between ... DUMMY ... and ... enrico-sorichetti JCL & VSAM 0 Mon Oct 17, 2016 4:31 pm
No new posts Allocate dataset withour BLKSIZE Susanta CLIST & REXX 2 Thu Sep 22, 2016 11:51 am


Facebook
Back to Top
 
Mainframe Wiki | Forum Rules | Bookmarks | Subscriptions | FAQ | Tutorials | Contact Us