I had to do some testing. I cooked up the below JCL to create a temporary data
set with no I/O and pass it to another step for input. I inserted store class
NOVIO because otherwise the data set was created on VIO, which clouded the
issue. Job messages indicate that the data set did get created on DASD and
passed to the second step.
The important point is that it does not get an I/O error trying to read
garbage. It gets immediate EOF, same as with a cataloged data set:
IGD101I SMS ALLOCATED TO DDNAME (TEMPFILE)
DSN (SYS19221.T152903.RA000.TESTALLO.R0475053 )
STORCLAS (NOVIO) MGMTCLAS ( ) DATACLAS (STAND1)
VOL SER NOS= ATMP05
IEF142I TESTALLO ALLOC - STEP WAS EXECUTED - COND CODE 0000
IGD106I SYS19221.T152903.RA000.TESTALLO.R0475053 PASSED, DDNAME=TEMPFILE
...
IGD103I SMS ALLOCATED TO DDNAME SYSUT1
IEF142I TESTALLO PRINT - STEP WAS EXECUTED - COND CODE 0000
IGD105I SYS19221.T152903.RA000.TESTALLO.R0475053 DELETED, DDNAME=SYSUT1
+-------------------------------------------------------------------------------
| --TIMINGS (MINS.)--
| JOBNAME STEPNAME PROCSTEP RC EXCP CONN TCB SRB CLOCK SERV PG
| TESTALLO PRINT 00 23 10 .00 .00 .0 135 0
|
| DDNAME UNIT TYPE BLKSIZ EXCP (ONLY NON-ZERO COUNTS LISTED)
|
| SYSUT1 741F 3390 18400 1
+-------------------------------------------------------------------------------
//ALLOC EXEC PGM=IEFBR14
//TEMPFILE DD SPACE=(CYL,1),DCB=SYS1.PROCLIB,DISP=(,PASS),
// STORCLAS=NOVIO
//*
//*
//PRINT EXEC PGM=IEBGENER
//SYSPRINT DD SYSOUT=*
//SYSIN DD DUMMY
//SYSUT2 DD DUMMY
//SYSUT1 DD DSN=*.ALLOC.TEMPFILE
.
.
J.O.Skip Robinson
Southern California Edison Company
Electric Dragon Team Paddler
SHARE MVS Program Co-Manager
323-715-0595 Mobile
626-543-6132 Office ⇐=== NEW
[email protected]
-----Original Message-----
From: IBM Mainframe Discussion List <[email protected]> On Behalf Of
Seymour J Metz
Sent: Friday, August 9, 2019 8:45 AM
To: [email protected]
Subject: (External):Re: CPU time cost of dynamic allocation
Believe what you want, but the fact is that DISP=NEW for DASD physically
creates a dataset. whether it also writes an EOF depends on how you're
configured.
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
________________________________________
From: IBM Mainframe Discussion List <[email protected]> on behalf of CM
Poncelet <[email protected]>
Sent: Thursday, August 8, 2019 6:52 PM
To: [email protected]
Subject: Re: CPU time cost of dynamic allocation
FWIW I hesitate to believe that PASSED/DELETED implies that the temp datasets
were ever physically created on DASD - unless they were OPENed for OUTPUT
in-between. I think the *physical* alloc happens only on an OPEN DCB with
MACRF=(PM/L).
Have you tried something like the following with IEFBR14?
'//WHATEVER DD DISP=(,CATLG),
'// DSN=<whatever>,
'// DCB=(RECFM=VBA,LRECL=137,BLKSIZE=27998,DSORG=PS),
'// SPACE=(CYL,(9999,2000)),VOL=(,,,20)
The VOL=(,,,20) would give you 320 extents. The SPACE=(CYL,9999) would
hopefully be unable to allocate the primary 9999 CYLs on the first 16 extents,
so would have to allocate the remaining CYLs on second/third/etc. DASD volumes.
An ISPF "3.2" would show on which VOLSERs the dataset had been allocated. An
ISPF "3.4" with "V" (if memory serves), and specifying the first VOLSER from
the "3.2", would then show how much free space and how many extents were still
available on it. If no free space or extents are left on it, do a "3.4" but now
specifying the fully qualified DSN *and* the second VOLSER from "3.2".
If some of the dataset has been physically allocated on this second DASD
VOLSER, the "3.4" should display it; else, it has not been physically allocated
on this DASD.
Just my ha'penny.
On 08/08/2019 20:17, Charles Mills wrote:
> I see
>
> IEF285I SYS19218.T143507.RA000.xxx00114.R0105346 PASSED
> IEF285I SYS19218.T143507.RA000.xxx00114.R0105347 PASSED
> IEF285I SYS19218.T143507.RA000.xxx00114.R0105348 PASSED
> ...
>
> And
>
> IEF285I SYS19218.T143507.RA000.xxx00114.R0105346 DELETED
> IEF285I SYS19218.T143507.RA000.xxx00114.R0105347 DELETED
> IEF285I SYS19218.T143507.RA000.xxx00114.R0105348 DELETED
> ...
>
> So it looks to me like DSCBs were actually created.
>
> Charles
>
>
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:[email protected]]
> On Behalf Of CM Poncelet
> Sent: Wednesday, August 7, 2019 12:34 PM
> To: [email protected]
> Subject: Re: CPU time cost of dynamic allocation
>
> >From years ago, I *think* an IEFBR14 step with DISP=(,CATLG) [or
> (,PASS)] does not physically allocate a dataset on a VOLSER but only
> registers it in the usercat. Have you checked whether it is in the VTOC?
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