Hi Martin,
These data sets are allocated by zSecure, so I would have to enquire of them
whether they attempt to multitask their allocations. My rather old history
tells me that allocation used to serialise quite substantially, thus making any
subtask allocation process wait, but maybe things are different now.
Lennie
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Martin Packer
Sent: 10 December 2024 13:50
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: DYNAMNBR
As a matter of interest, Lennie, are these data sets allocated and de-allocated
sequentially, or all at the same time? Question to others: Does that matter in
terms of (X)TIOT slots?
Cheers, Martin
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of
Lennie Bradshaw <lennie-brads...@outlook.com>
Date: Tuesday, 10 December 2024 at 13:45
To: IBM-MAIN@LISTSERV.UA.EDU <IBM-MAIN@LISTSERV.UA.EDU>
Subject: [EXTERNAL] Re: DYNAMNBR
Scott,
Thanks again for the detail.
Firstly a couple of questions.
1. Can XTIOT only be requested by using Dynamic Allocation?
2. Is XTIOT only available to authorised callers?
Looking at the allocation failures in question I have,
IEFA111I JJJJJJJJ IS USING THE FOLLOWING JOB RELATED SETTINGS:
SWA=ABOVE, TIOT SIZE=64K,DSENQSHR=DISALLOW,GDGBIAS=JOB
At the failure I have,
IKJ56220I DATA SET -----REDACTED----- NOT ALLOCATED, TOO MANY DATA SETS+
IKJ56220I MAXIMUM NUMBER OF DATA SET ALLOCATIONS ALLOWED BY YOUR SESSION HAS
BEEN REACHED, YOU SHOULD FREE UNUSED DATA SETS.
This was a batch job requesting allocation of 312 similar data sets. The count
of IGD103I messages indicates 257 were allocated. Crucially I see all these
data sets were allocated with a DATACLAS value which has a DVC of 59.
So while I cannot reconcile the numbers of allocated datasets with the number
of TIOT slots (257 x 59 = 15163 and 15163 > 3273) I think the DVC is likely to
be the cause of the problem.
Looks like I have no way of changing the DATACLAS used for those allocations;
It cannot be overridden nor can it be changed.
So it looks like the only way to handle these datasets is to copy them using a
different DATACLAS.
Does that look correct to you?
Lennie
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Scott Ballentine
Sent: 09 December 2024 14:05
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: DYNAMNBR
I'll throw a few more random things out here that might be helpful.
S99ERROR code x'043C' indicates that the DYNAMNBR value is being exceeded. If
you're getting a different error... then it's probably not worth digging around
this value.
Allocation requests that ask for an XTIOT don't take space from the 64K (or
smaller) TIOT. Also it's a good idea to request DSABs above-the-line and
actual UCBs, otherwise you end up with a lot of control blocks in 24-bit
storage. There are a few ways to do this, but the easiest is to set the
S99DXACU flag in the S99RB - that gives you all three of those options. Also
make sure the job class has SWA=ABOVE.
Take a look at the number of data sets that are able to be allocated at one
time. You can make some guesses about what limit you're running into based on
that. The TIOT can hold a maximum of 3273 DDs (and less if they are
multi-volume data sets or a DVC is in use.) If they're getting past that limit
(maybe into the tens of thousands of allocations), it's more likely that these
are XTIOT requests, but some of the other control blocks (such as the DSABs)
are going into 24-bit storage.
-Scott Ballentine
IBM z/OS Device Allocation
sbal...@us.ibm.com
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