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Regarding SPACE parameter in JCL

 
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rksenthil2003

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PostPosted: Wed Sep 19, 2007 7:19 pm    Post subject: Regarding SPACE parameter in JCL
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Suppose the space parameter is coded as

SPACE=(REC-LENGTH,(PRI,SEC),RLSE)

Eg: SPACE=(1470,(100,50),RLSE)

How to calculate the maximum number of bytes or tracks that will be used by the system?
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Raphael Bacay

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PostPosted: Wed Sep 19, 2007 7:50 pm    Post subject:
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I looked and found that there are

1 track = 56664 bytes.
1 cylinder = 15 tracks

In your jcl you have 100 cylinders primary and
50 secondary. You can have 11 extents of secondary storage
so you have 100 * 15 * 56664 + 50 * 11 * 15 * 56664 bytes of
maximum storage.
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rksenthil2003

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PostPosted: Wed Sep 19, 2007 8:36 pm    Post subject: Reply to: Regarding SPACE parameter in JCL
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Is it applicale even if record length is given as the first parameter in the SPACE?
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Raphael Bacay

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PostPosted: Wed Sep 19, 2007 8:39 pm    Post subject:
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I am afraid so.
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dick scherrer

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PostPosted: Wed Sep 19, 2007 8:46 pm    Post subject:
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Hello,

Quote:
Is it applicale even if record length is given as the first parameter in the SPACE?
The example you posted is block length, not record length. Look here http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/handheld/Connected/BOOKS/iea2b650/12.55.2.1?SHELF=&DT=20040712170508&CASE=for the reason why. This is from the JCL manual available via the "Manuals" link at the top of the web page. You might hav meant to use record length, but the way it is coded it specifies block size.

I'd suggest you talk with your storage management people as there are different types of dasd units with different capacities and they will know the specifics about your system.
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expat

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PostPosted: Wed Sep 19, 2007 9:45 pm    Post subject:
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Raphael Bacay wrote:

You can have 11 extents of secondary storage

The number quoted by IBM for secondary space extents is 15, however this does rather depend on the fragmentation of the DASD volume being used.

Each allocation, i.e. primary and secondary, may consist of up to 5 extents. Therefor if you have an allocation of (CYL,(100,50),RLSE) the primary allocation of 100 cylinders may be fragmented into 5 extents, so now you only have 11 extents left for secondary allocations.

Assume a badly fragmented DASD and the first of the secondary allocations consists of 3 extents, the next secondary of 4 extents, and the next also of four extents.

You now have used up the maximum number of extents for the dataset, although you have only allocated one primary and three secondary allocations, 100 + (3 * 50) = 250 cylinders.

The expected allocation was 100 + (15 * 50) = 850 cylinders.

But now back to the original question -

Let's assume an LRECL 0f 100 for a FB file, with 100,000 records.

27998 / 100 = 27900, which is the optimum blocksize for a 3390 DASD.
This means that we get 279 records per block and two blocks on each track. So 558 records on each track.

100,000 / 558 = 179.21 (rounded up to) 180 tracks of used space.

180 / 15 = 12 cylinders of used DASD space.
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sunilkumarchandramohan

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PostPosted: Wed Oct 07, 2009 10:10 am    Post subject: Calculating space parameter for PS files
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The space can be calculated if AVGREC=K

Space=(lrecl,(pri,sec),RLSE)

then

primary = lrecl*pri kilobytes

secondary = lrecl*sec kilobytes

use following conversion formulae to calculate the space in tracks or cylinders:
1 track=56664 bytes

1 cylinder = 15 tracks
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Anuj Dhawan

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PostPosted: Wed Oct 07, 2009 10:40 am    Post subject:
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Quote:
Waiting for your earliest reply
There is not much fun in re-opening such old threads...
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expat

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PostPosted: Wed Oct 07, 2009 11:30 am    Post subject: Re: Calculating space parameter for PS files
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Any reason for awakening a two year old thread ?

expat wrote:
sunilkumarchandramohan wrote:
The space can be calculated if AVGREC=K
Space=(lrecl,(pri,sec),RLSE)
then
primary = lrecl*pri kilobytes
secondary = lrecl*sec kilobytes
use following conversion formulae to calculate the space in tracks or cylinders:
1 track=56664 bytes
1 cylinder = 15 tracks

The DASD allocation routines will ALWAYS convert space allocations into either TRLS or CYLS.

It seems to me that IBM may have introduced these so called easy space allocation methods for those too lazy or too dumb to figure it out fairly accurately for themselves icon_rolleyes.gif
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sunilkumarchandramohan

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PostPosted: Fri Oct 09, 2009 1:41 pm    Post subject:
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Expat,
just to provide a information for calculating space since many of us use these type of methods for calculating.
Apart from this its just an informative message
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expat

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PostPosted: Fri Oct 09, 2009 2:04 pm    Post subject:
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Please look at THIS previous thread.
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