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
 

 

To allocate cylinders to a dataset

 
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> JCL & VSAM
View previous topic :: :: View next topic  
Author Message
meenakshi_forum
Warnings : 1

Active User


Joined: 27 May 2008
Posts: 121
Location: India

PostPosted: Fri Apr 16, 2010 7:01 am    Post subject: To allocate cylinders to a dataset
Reply with quote

Hi,

How do we determine the number of cylinders to be allocated to a dataset?

Please give me an example.

Thanks!
Back to top
View user's profile Send private message

CICS Guy

Senior Member


Joined: 18 Jul 2007
Posts: 2150
Location: At my coffee table

PostPosted: Fri Apr 16, 2010 8:03 am    Post subject:
Reply with quote

Number or records and block size and blocks per track and tracks per cylinders...
Quote:
Please give me an example.

How many records?
Whay is the block size?
How many blocks will fit on a track?
How many tracks do a cylinder make?

Please give me an example.
Back to top
View user's profile Send private message
Robert Sample

Global Moderator


Joined: 06 Jun 2008
Posts: 7993
Location: Bellevue, IA

PostPosted: Fri Apr 16, 2010 8:03 am    Post subject:
Reply with quote

Find out how many records will be in the file, adjust for added records over time, and use the formulas to convert records to cylinders.

If you search this forum, you will find many examples of space calculations.
Back to top
View user's profile Send private message
ridgewalker58

New User


Joined: 26 Sep 2008
Posts: 51
Location: New York

PostPosted: Sat Apr 17, 2010 7:23 am    Post subject:
Reply with quote

The Disks that we work with contain approx 57000 bytes per track and 20 tracks per cylinder. Your maximum block size can be 32768 bytes. So when I need to calculate most efficient space I usually try to stay around a DIVISABLE of 32000 bytes.
Back to top
View user's profile Send private message
Robert Sample

Global Moderator


Joined: 06 Jun 2008
Posts: 7993
Location: Bellevue, IA

PostPosted: Sat Apr 17, 2010 7:42 am    Post subject:
Reply with quote

3390 disk drives have 56,664 bytes per track and 15 tracks per cylinder (see the 3390 reference card SX26-4577 for more details). The least wasteful block size is 27,998 bytes which allows 2 blocks per track. If you want to minimize wasted space, go with a block size close to 27,998. If you go over 27,998 you only get one block per track so using 32000 bytes per block as ridgewalker58 recommends actually reduces the amount of data that can be stored on the disk by nearly half.

Very recent releases of z/OS now allow large block sequential files which can go over 32767 bytes per block, but using this would depend upon the release of the operating system.
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 Unable to catalog a gdg dataset resid... Shovan JCL & VSAM 4 Fri Mar 24, 2017 2:24 pm
No new posts Want to pull the job log into a Mainf... Jishu Mukherjee Compuware & Other Tools 9 Tue Mar 21, 2017 4:48 pm
No new posts JCL to get submitted once dataset has... vinu78 JCL & VSAM 17 Thu Feb 16, 2017 7:32 am
No new posts FTP - JCL failed while passing FTP co... Suneetha1612 JCL & VSAM 12 Wed Nov 16, 2016 7:33 pm
No new posts To trim spaces in a pipe delimited da... Nish84 COBOL Programming 16 Mon Oct 10, 2016 1:54 pm


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