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
 

 

Space requirement question

 
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> JCL & VSAM
View previous topic :: :: View next topic  
Author Message
fahir83

New User


Joined: 27 Jan 2006
Posts: 22

PostPosted: Tue Sep 15, 2009 9:53 pm    Post subject: Space requirement question
Reply with quote

Hi

I had a space issue with one of my new dataset creation. I have corrected it by allocating more space. Below is my jcl

UNIT=SYSDA,MGMTCLAS=MB000804,
SPACE=(10796,(7500,10),RLSE),
VOL=(,,,20),
DCB=(SYS3.DSCB,DSORG=PS,
RECFM=FB,LRECL=611,BLKSIZE=0)

The total of records is 400000. as i already know the calculation, i have calculated using 27998/611=46 rec/block. no.of.rec/46 = 8696 blocks. so i have allocated more SPACE=(10796,(10000,100),RLSE) for a safer side and resolved the issue. But my question is what is the role block length (10796) playing here? whether i need to bother abt 10796?
Back to top
View user's profile Send private message

dick scherrer

Site Director


Joined: 23 Nov 2006
Posts: 19270
Location: Inside the Matrix

PostPosted: Tue Sep 15, 2009 10:25 pm    Post subject:
Reply with quote

Hello,

When you allocate space, you need to specify how space will be allocated (often trk or cyl). You have used blksize.
Back to top
View user's profile Send private message
fahir83

New User


Joined: 27 Jan 2006
Posts: 22

PostPosted: Tue Sep 15, 2009 10:34 pm    Post subject:
Reply with quote

Thats True Dick. But my question is whether 10796 will be having any effect on space calculation? whether i need to consider that as an parameter while calculating space? As i mentioned BLKSIZE = 0, it will take the optimum block size, But just want to clarify and to be clear.
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: Tue Sep 15, 2009 10:42 pm    Post subject:
Reply with quote

Quote:
27998/611=46 rec/block. no.of.rec/46 = 8696 blocks
Your calculation is based on half-track blocking (27998 bytes maximum per block). Your selected block size gives 17 records per block. 400,000 records divided by 17 gives 23,530 blocks required -- not the mere 10,000 you allocated.

Also, 10796 is not evenly divided by 611. You should be using 10387 instead (or 10998?) to be evenly divisible.

I suspect this is an SMS-managed data set and the BLKSIZE=0 is overriding your specified block size. If this data set were going to a non-SMS volume, you would be getting an abend stating that block size is not a multiple of LRECL.

In order to prevent future confusion, change the 10796 to TRK or CYL and adjust the allocation number appropriately.
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 VSAM Space Allocation mrgnndhmk JCL & VSAM 7 Sat Apr 22, 2017 12:42 am
No new posts QUESTION: RETURN CHANNEL pahiker CA Products 21 Thu Apr 20, 2017 12:31 am
No new posts The Last Two Question For You To Ask ... CaptBill Mainframe Interview Questions 0 Fri Apr 14, 2017 5:42 am
This topic is locked: you cannot edit posts or make replies. Need help in estimating space of unlo... ashek15 IMS DB/DC 12 Fri Apr 07, 2017 5:11 am
No new posts Need inputs on Space requirement and... ashek15 IMS DB/DC 0 Sat Apr 01, 2017 8:26 am


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