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MQSeries.net Forum Index » General IBM MQ Support » purpose of subpool.lck file

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smvineed
PostPosted: Wed Aug 17, 2016 1:54 am    Post subject: purpose of subpool.lck file Reply with quote

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Joined: 24 Jul 2011
Posts: 34

Could you please explain the use of subpool.lck in /var/mqm/sockets/XXX/qmgrlocal/hostname?
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mqjeff
PostPosted: Wed Aug 17, 2016 3:48 am    Post subject: Reply with quote

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Joined: 25 Jun 2008
Posts: 17447

It's a lock file.
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Vitor
PostPosted: Wed Aug 17, 2016 4:24 am    Post subject: Re: purpose of subpool.lck file Reply with quote

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smvineed wrote:
Could you please explain the use of subpool.lck in /var/mqm/sockets/XXX/qmgrlocal/hostname?


It's nothing you should be worrying about or fiddling with.

It belongs to the software and you shouldn't be playing with its toys.
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bruce2359
PostPosted: Wed Aug 17, 2016 1:09 pm    Post subject: Re: purpose of subpool.lck file Reply with quote

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Joined: 05 Jan 2008
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Location: US: west coast, almost. Otherwise, enroute.

smvineed wrote:
Could you please explain the use of subpool.lck in /var/mqm/sockets/XXX/qmgrlocal/hostname?

A general explanation follows:

Locks are used in multi-user (server) software to provide serialized access to important resources - in this instance virtual storage. A subpool is an area of virtual storage reserved for some specific purpose - for example: holding database rows, or messages in queues.

The contents of a subpool may require that it is only accessed by one "user" at a time. The subpool lock must first be acquired before the resource it protects can be accessed.

For MQ queues, some users may be browsing messages, others may be destructively consuming messages. Some mechanism must be in place to ensure that no two (or more) concurrent users are trying to destructively consume the same message at the same time. Locks provide this mechanism.

As it relates to IP network traffic, the socket() calls read or write into buffers (subpools). To keep multiple listeners writers from overwriting IP packets as they sit in buffers, the buffers are protected by locks.
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gbaddeley
PostPosted: Wed Aug 17, 2016 5:41 pm    Post subject: Reply with quote

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Joined: 25 Mar 2003
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Location: Melbourne, Australia

I have experienced MQ FixPack installation failures like:

"Verifying selections...You seem to have an MQ queue manager still running. You must stop all MQ processing, and stop the Queue Manager(s) by using the endmqm command before trying to install/update/delete the MQ product."

There was no actual qmgr running at the time. The solution is to remove the subpool.lck file:
rm /var/mqm/sockets/<qmgr name>/qmgrlocl/<hostname>/subpool.lck

A new file is created when the qmgr starts. This is the only interaction I have ever had with this file over 20 years of MQ tech support.
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mqjeff
PostPosted: Thu Aug 18, 2016 3:33 am    Post subject: Reply with quote

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gbaddeley - Is it in any way possible that either some MQ process was still running, or had ended/crashed badly?

I know that in general you would not fail to check these things, but one always has those days...

Particularly when one hasn't had enough coffee... yes, Vitor?
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Vitor
PostPosted: Thu Aug 18, 2016 6:00 am    Post subject: Reply with quote

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mqjeff wrote:
gbaddeley - Is it in any way possible that either some MQ process was still running, or had ended/crashed badly?

I know that in general you would not fail to check these things, but one always has those days...

Particularly when one hasn't had enough coffee... yes, Vitor?



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gbaddeley
PostPosted: Thu Aug 18, 2016 5:53 pm    Post subject: Reply with quote

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mqjeff wrote:
gbaddeley - Is it in any way possible that either some MQ process was still running, or had ended/crashed badly?

There were no mqm processes running, dspmq showed the qmgr as ended normally, running amqiclen did not help.
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mqjeff
PostPosted: Fri Aug 19, 2016 3:49 am    Post subject: Reply with quote

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gbaddeley wrote:
mqjeff wrote:
gbaddeley - Is it in any way possible that either some MQ process was still running, or had ended/crashed badly?

There were no mqm processes running, dspmq showed the qmgr as ended normally, running amqiclen did not help.


As I said, I know in general that you would check these things. Seems very odd, though, that this file would still exist. I could speculate on several reasons, but I don't think that's terribly productive at this point, and the coffee hasn't kicked in yet.

I'd still not recommend that *anyone* muck with this file outside the scope of a PMR.
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smvineed
PostPosted: Fri Aug 19, 2016 4:06 am    Post subject: purpose of subpool.lck file Reply with quote

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Joined: 24 Jul 2011
Posts: 34

Thank you all for the explanations
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