Discussion:
SVCDUMP consideration
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Jake Anderson
2017-08-08 09:24:10 UTC
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Hi

Is there any constraint when we are taking SVCDUMP ? Are there any CPU
spike due to SVCDUMP ?

Generally what are the factors needs to be considered while taking SVCDUMP ?

Jake

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Vernooij, Kees - KLM , ITOPT1
2017-08-08 09:34:30 UTC
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Have a look at the Q= SDUMP option, this specifies if the system will be quiesced while dumping common storage.
Command: D DUMP,O.

Kees.
-----Original Message-----
Behalf Of Jake Anderson
Sent: 08 August, 2017 11:25
Subject: SVCDUMP consideration
Hi
Is there any constraint when we are taking SVCDUMP ? Are there any CPU
spike due to SVCDUMP ?
Generally what are the factors needs to be considered while taking SVCDUMP ?
Jake
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Elardus Engelbrecht
2017-08-08 10:25:23 UTC
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Is there any constraint when we are taking SVCDUMP ? Are there any CPU spike due to SVCDUMP ?
It depends. Sometimes you get a CPU spike or something slows down your system. YMMV of course.

It also depends on how the application or job is handling the dump itself.
Generally what are the factors needs to be considered while taking SVCDUMP ?
Check Kees good reply to you. The command he gave is a good starting point.

Also look in your PARMLIB to see how your DD and CD commands are setup. These commands are usually in COMMNDxx or IEACMDxx.

Depending on the dump, you may need to add the right DD statement to your STC or job ___before__ taking a dump.

Are you also going to set a SLIP?

Groete / Greetings
Elardus Engelbrecht

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Jake Anderson
2017-08-08 13:45:46 UTC
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Hi

General questions. Since when we set SAD for zOS we keep that based on the
size of Real storage.

When we are setting up an SVCDUMP for a particular product. How does that
dumping takes place ? Is it only the control block occupied by the specific
product ? Or it scans the entire RSM dedicated to the OS ?

On 08-Aug-2017 3:56 PM, "Elardus Engelbrecht" <
Post by Jake Anderson
Post by Jake Anderson
Is there any constraint when we are taking SVCDUMP ? Are there any CPU
spike due to SVCDUMP ?
It depends. Sometimes you get a CPU spike or something slows down your
system. YMMV of course.
It also depends on how the application or job is handling the dump itself.
Post by Jake Anderson
Generally what are the factors needs to be considered while taking
SVCDUMP ?
Check Kees good reply to you. The command he gave is a good starting point.
Also look in your PARMLIB to see how your DD and CD commands are setup.
These commands are usually in COMMNDxx or IEACMDxx.
Depending on the dump, you may need to add the right DD statement to your
STC or job ___before__ taking a dump.
Are you also going to set a SLIP?
Groete / Greetings
Elardus Engelbrecht
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Lizette Koehler
2017-08-08 13:52:58 UTC
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SVCDUMPs can go to SYS1.DUMPx or a dynamic allocation based on your settings in z/OS

Look at the mvs command for Dump Datasets (DD) for what your shop is using.

See this link: https://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.ieag100/dumpds.htm


SVC Dumps can contain as much or as little as specified. Some products dump a large amount of control blocks (Think DB2)

So just a few.

The Dump process has a Dataspace it dumps to. So the process is fast. Once the Dump goes to the dataspace, it is then dumped to your designated SVC Dump dataset

A quick search on the www.ibm.com for SVCDUMP DD pulls up this link

https://www.ibm.com/support/knowledgecenter/SSLTBW_2.1.0/com.ibm.zos.v2r1.ieav100/seqdat.htm

It should be a good starting point.

How SVCDUMP behaves is going to be dependent on how you have it set up. There is not a one size fits all process.

Lizette
-----Original Message-----
Behalf Of Jake Anderson
Sent: Tuesday, August 08, 2017 6:47 AM
Subject: Re: SVCDUMP consideration
Hi
General questions. Since when we set SAD for zOS we keep that based on the
size of Real storage.
When we are setting up an SVCDUMP for a particular product. How does that
dumping takes place ? Is it only the control block occupied by the specific
product ? Or it scans the entire RSM dedicated to the OS ?
On 08-Aug-2017 3:56 PM, "Elardus Engelbrecht" <
Post by Jake Anderson
Post by Jake Anderson
Is there any constraint when we are taking SVCDUMP ? Are there any CPU
spike due to SVCDUMP ?
It depends. Sometimes you get a CPU spike or something slows down your
system. YMMV of course.
It also depends on how the application or job is handling the dump itself.
Post by Jake Anderson
Generally what are the factors needs to be considered while taking
SVCDUMP ?
Check Kees good reply to you. The command he gave is a good starting point.
Also look in your PARMLIB to see how your DD and CD commands are setup.
These commands are usually in COMMNDxx or IEACMDxx.
Depending on the dump, you may need to add the right DD statement to
your STC or job ___before__ taking a dump.
Are you also going to set a SLIP?
Groete / Greetings
Elardus Engelbrecht
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Peter Relson
2017-08-09 11:19:58 UTC
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Are there any CPU spike due to SVCDUMP ?
Of course there is. An SVC Dump takes a lot of cycles. And of course there
is a spike in the consumption of frames needed to capture the data
(whether that is real or auxiliary storage). z/OS attempts to make sure
that this frame consumption does not have a significantly adverse affect
on the rest of the system.
Generally what are the factors needs to be considered while taking
SVCDUMP

I'd think that your primary consideration is to try to make sure that SVC
Dump is capturing the data that you need it to capture to diagnose the
problem for which you are taking the dump, via such keywords as LIST,
SUMLST, and SDATA.

In general, the system is set non-dispatchable until SVC Dump captures
(not writes to data set) common storage, and the individual address
space(s) being dumped are set non-dispatchable until their storage is
captured. As with just about everything, there are exceptions. But if you
want a "good" dump (i.e., one with consistent data), those things will
have to happen

Peter Relson
z/OS Core Technology Design


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