Temporary Data Sets

[Buckton, T. , Theo]

Hi,

Can somebody direct me to documentation on temporary data sets. I need to understand the characteristics and restrictions of these &&TEMP data sets:
Space limits;
Can it extend over more than 1 volume if so, would a multi-volume temp data set pose a problem if it is referenced again by a different DD statement in the same job step?

Regards
Theo
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[Blaicher, Christopher Y.]

Temporary data sets are just like permanent data sets, they just go away at the end of the step if you specify DISP=(NEW,DELETE), or at the end of the job if you specify DISP=(NEW,PASS).

Chris Blaicher
Technical Architect
Mainframe Development
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E: ***@syncsort.com

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-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-***@LISTSERV.UA.EDU] On Behalf Of Buckton, T. (Theo)
Sent: Tuesday, October 3, 2017 9:39 AM
To: IBM-***@LISTSERV.UA.EDU
Subject: Temporary Data Sets

Hi,

Can somebody direct me to documentation on temporary data sets. I need to understand the characteristics and restrictions of these &&TEMP data sets:
Space limits;
Can it extend over more than 1 volume if so, would a multi-volume temp data set pose a problem if it is referenced again by a different DD statement in the same job step?

Regards
Theo
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[Paul Gilmartin]

Post by Buckton, T. , Theo
Space limits;
Can it extend over more than 1 volume if so, would a multi-volume temp data set pose a problem if it is referenced again by a different DD statement in the same job step?

The JCL Ref. says:

REF=*.ddname
...
| VOL=REF obtains the volume serial numbers ...

I assume use of plural implies multiple volumes are supported.

| from the referenced ... earlier DD statement. ...
| No other information is retrieved by VOL=REF; in particular it does not obtain
| the volume sequence number, volume count, or data set sequence number.

Ugh. So the programmer must keep the data set sequence number on a
sticky note on a desktop.

But I suppose that VOL=REF is superfluous for catalogued data sets and
that multiple temp data sets are rarely stacked on volumes.

-- gil

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[Steve Smith]

He would use a DSN referback, not VOL=REF. And no, multi-volume isn't
an issue. As C. Blaicher said above, the only difference is the
system generates the DSN, and tries to get rid of the dataset
automatically.

sas

N.B. By "DSN" I mean "dataset name", not "dataset". Which I'm annoyed
I have to say.

On Tue, Oct 3, 2017 at 9:55 AM, Paul Gilmartin

Post by Paul Gilmartin

Post by Buckton, T. , Theo
Space limits;
Can it extend over more than 1 volume if so, would a multi-volume temp data set pose a problem if it is referenced again by a different DD statement in the same job step?

REF=*.ddname
...
| VOL=REF obtains the volume serial numbers ...
I assume use of plural implies multiple volumes are supported.
| from the referenced ... earlier DD statement. ...
| No other information is retrieved by VOL=REF; in particular it does not obtain
| the volume sequence number, volume count, or data set sequence number.
Ugh. So the programmer must keep the data set sequence number on a
sticky note on a desktop.
But I suppose that VOL=REF is superfluous for catalogued data sets and
that multiple temp data sets are rarely stacked on volumes.
-- gil
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[Tom Marchant]

Post by Buckton, T. , Theo
Can somebody direct me to documentation on temporary data sets.
I need to understand the characteristics and restrictions of these
Space limits;
Can it extend over more than 1 volume

AFAIK there are no special limits for temporary data sets that are
imposed by the system, but there may be restrictions imposed by
the way SMS is set up in your shop. Check with your storage
administrators.

[Tom Marchant]

Post by Steve Smith
He would use a DSN referback, not VOL=REF. And no, multi-volume isn't
an issue. As C. Blaicher said above, the only difference is the
system generates the DSN, and tries to get rid of the dataset
automatically.

IIRC, when referring to a temporary data set in another DD statement
in the same step, VOL=REF is required.

[R.S.]

Post by Buckton, T. , Theo
Hi,
Space limits;
Can it extend over more than 1 volume if so, would a multi-volume temp data set pose a problem if it is referenced again by a different DD statement in the same job step?

There are no such (as above) disadvantages/restrictions of using temp
datasets. However, if you're afraid of it, just get rid of temp, and use
regular MVS dataset with DISP=DELETE on last DD referencing to it.

BTW: In case of multi-step temp DS one can use VOL=REF of DSN=&&SOME.
IMHO the last one is much more convenient.
--
Radoslaw Skorupka
Lodz, Poland




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[Lizette Koehler]

What problem are you seeing with TEMP datasets?

Is it something your storage admin might have in the ACS Code that is causing an issue?

As others have stated, just like Named datasets. Just goes away at step or job end depending on the JCL.


Lizette

Post by Blaicher, Christopher Y.
-----Original Message-----
Behalf Of Buckton, T. (Theo)
Sent: Tuesday, October 03, 2017 6:39 AM
Subject: Temporary Data Sets
Hi,
Can somebody direct me to documentation on temporary data sets. I need to
Space limits;
Can it extend over more than 1 volume if so, would a multi-volume temp data
set pose a problem if it is referenced again by a different DD statement in
the same job step?
Regards
Theo

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[Edward Finnell]

For decades MVS has honored the concept of public, Storage and private DASD. Numerous SHARE papers on how to configure DASD subsystems in order to reduce contention and optimize thruput. WSC under Ray Wicks produced many of them. One of my favorites was the 'The Big Pitcher'. Properly administered SMS can enhance the basic concepts and augment them with storage overflow.
 
If we had more info on the problem better suggestions could be provided. One of the old tricks was to preallocate sortwks and pass them thru the life of the job. No need to worry about vol=ref
 
In a message dated 10/3/2017 12:57:45 PM Central Standard Time, ***@MINDSPRING.COM writes:

 
As others have stated, just like Named datasets. Just goes away at step or job end depending on the JCL.

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[Anne & Lynn Wheeler]

Post by Edward Finnell
For decades MVS has honored the concept of public, Storage and private
DASD. Numerous SHARE papers on how to configure DASD subsystems in
order to reduce contention and optimize thruput. WSC under Ray Wicks
produced many of them. One of my favorites was the 'The Big
Pitcher'. Properly administered SMS can enhance the basic concepts and
augment them with storage overflow.
 
If we had more info on the problem better suggestions could be
provided. One of the old tricks was to preallocate sortwks and pass
them thru the life of the job. No need to worry about vol=ref

back when CKD were real ... (rather than various kinds of simulation on
industry fixed-block disks ... all that rotational positioning and arm
motion, track lengths ... are all fiction) ... I was increasingly
pointing out that disk wasn't keeping up with computer technology and by
the early 80s was saying that disk relative system throughput had
declined by a factor of ten times since the 60s (disk throughput
increased 3-5 times, processor and memory throughput increased 40-50
times).

Some disk division executive took exception and assigned the division
performance group to refute the statements. after several weeks they
eventually came back and effectively said that I had slightly under
stated the problem. The analysis was then respun as disk configuration
recommendations for improving system throughput ... SHARE presentation
B874. old post with part of the early 80 comparison
http://www.garlic.com/~lynn/93.html#31
old posts with pieces of B874
http://www.garlic.com/~lynn/2001l.html#56
http://www.garlic.com/~lynn/2006f.html#3

note that memory is the new disk ... current latency for cache miss,
memory access ... when measured in count of processor cycles is similar
to 60s disk latency when measured in 60s processor cycles .... it is
part of the introduction of out-of-order execution, branch prediction,
speculative execution, hyperthreading ... stuff that can go on while
waiting on stalled instruction (waiting for memory on cache miss)
.... these show up in z196 (accounting for at least half the performance
improvement over z10) ... much of this stuff have been in other
platforms for decades.

trivia: 195 pipeline had out-of-order execution ... but no branch
prediction and/or speculative execution ... so conditional branches
stalled the pipeline, most applications would only ran at half 195 rated
performance. I got dragged into proposal to hyperthread 195 ... two
instruction streams simulating multiprocessor ... two simulated
processors running programs around half throughput ... then would keep
195 running at rated speed. It was never done ...

IBM hyper/multi threading patents mentioned in this post about the end
of ACS/360
https://people.cs.clemson.edu/~mark/acs_end.html

from Amdahl interview in the above:

IBM management decided not to do it, for it would advance the computing
capability too fast for the company to control the growth of the
computer marketplace, thus reducing their profit potential. I then
recommended that the ACS lab be closed, and it was.

... snip ...

end of the article has some of the acs/360 features that show up more
than 20yrs later in es/9000.

[Paul Gilmartin]

Post by Edward Finnell
 
If we had more info on the problem better suggestions could be provided. One of the old tricks was to preallocate sortwks and pass them thru the life of the job. No need to worry about vol=ref
 

Temporary data sets are a major convenience; one of the few facilities of
Classic OS that I miss in UNIX. But the Passed Data Set Queue is a sorry
kludge. A smarter interpreter would simply keep temp data sets until the
last job step referencing them, then scratch them, similar to the processing
of data set ENQs nowadays. The programmer should be able to reference
a temp data set multiple times in a step without the VOL=REF circumvention.

I believe the current recommendation is not to preallocate sortwks; DFSORT
knows best.

-- gil

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