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bkiran2020
PostPosted: Wed Feb 22, 2017 3:42 am Post subject: logging Reply with quote

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Joined: 20 Jan 2011
Posts: 243
Location: US

How come when we have only CIRCULAR Logging available on Mainframe we still are able to access the Media Recovery Functionality of the QMGR. Only Linear Logging allows Media Recovery...
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bruce2359
PostPosted: Wed Feb 22, 2017 4:54 am Post subject: Reply with quote

Poobah

Joined: 05 Jan 2008
Posts: 8576
Location: US: west coast, almost. Otherwise, enroute.

What Media Recovery Functionality on IMQ for z/OS are you referring to specifically?
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bkiran2020
PostPosted: Wed Feb 22, 2017 5:34 am Post subject: Reply with quote

Master

Joined: 20 Jan 2011
Posts: 243
Location: US

bruce2359 wrote:
What Media Recovery Functionality on IMQ for z/OS are you referring to specifically?


To recreate the damage object.
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Vitor
PostPosted: Wed Feb 22, 2017 6:16 am Post subject: Re: logging Reply with quote

Grand High Poobah

Joined: 11 Nov 2005
Posts: 25904
Location: Texas, USA

bkiran2020 wrote:
How come when we have only CIRCULAR Logging available on Mainframe we still are able to access the Media Recovery Functionality of the QMGR. Only Linear Logging allows Media Recovery...


You're in error. The z/OS queue manager only uses linear logging; see here:

Quote:

BM MQ records all significant events as they occur in an active log. The log contains the information needed to recover:

Persistent messages
IBM MQ objects, such as queues
The IBM MQ queue manager


Now it does also say:

Quote:
The active log comprises a collection of data sets (up to 310) which are used cyclically.


If you read the rest of the entry, it then talks about the need to archive these logs and offload unneeded logs to tape or other secondary storage. It also talks about the dual logging used to ensure integrity.

The z/OS OS does not work the same way as another other OS like Windows or *NIX. The disc is arranged differently, system tasks run differently, the queue managers work differently. This is why a z/OS queue manager has storage classes and page sets for queue storage, concepts that don't exist elsewhere.
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gbaddeley
PostPosted: Wed Feb 22, 2017 3:57 pm Post subject: Re: logging Reply with quote

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Joined: 25 Mar 2003
Posts: 2056
Location: Melbourne, Australia

bkiran2020 wrote:
How come when we have only CIRCULAR Logging available on Mainframe we still are able to access the Media Recovery Functionality of the QMGR. Only Linear Logging allows Media Recovery...

z/OS mainframe MQ functions like LINEAR logging, although there are only a limited number of datasets that are used in a cyclic fashion. The trick is that as older logs are no longer required for active UOWs, the log dataset contents is offloaded to archive d dasd or tape, and it becomes available for use in the next cycle around.

On a busy qmgr it should take no less than about 10 minutes to cycle around all the log datasets. This gives enough time for the archives to occur.

If a full roll forward is requested on on cost start, the qmgr will access the archived logs.
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bkiran2020
PostPosted: Thu Feb 23, 2017 8:43 am Post subject: Re: logging Reply with quote

Master

Joined: 20 Jan 2011
Posts: 243
Location: US

gbaddeley wrote:
bkiran2020 wrote:
How come when we have only CIRCULAR Logging available on Mainframe we still are able to access the Media Recovery Functionality of the QMGR. Only Linear Logging allows Media Recovery...

z/OS mainframe MQ functions like LINEAR logging, although there are only a limited number of datasets that are used in a cyclic fashion. The trick is that as older logs are no longer required for active UOWs, the log dataset contents is offloaded to archive d dasd or tape, and it becomes available for use in the next cycle around.

On a busy qmgr it should take no less than about 10 minutes to cycle around all the log datasets. This gives enough time for the archives to occur.

If a full roll forward is requested on on cost start, the qmgr will access the archived logs.


Thanks :
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bruce2359
PostPosted: Thu Feb 23, 2017 2:20 pm Post subject: Re: logging Reply with quote

Poobah

Joined: 05 Jan 2008
Posts: 8576
Location: US: west coast, almost. Otherwise, enroute.

gbaddeley wrote:
bkiran2020 wrote:
How come when we have only CIRCULAR Logging available on Mainframe we still are able to access the Media Recovery Functionality of the QMGR. Only Linear Logging allows Media Recovery...

z/OS mainframe MQ functions like LINEAR logging, although there are only a limited number of datasets that are used in a cyclic fashion. The trick is that as older logs are no longer required for active UOWs, the log dataset contents is offloaded to archive d dasd or tape, and it becomes available for use in the next cycle around.

On a busy qmgr it should take no less than about 10 minutes to cycle around all the log datasets. This gives enough time for the archives to occur.

If a full roll forward is requested on on cost start, the qmgr will access the archived logs.


Planning for log size is well-documented. Part of the planning is having the appropriate (maximum) log extents in anticipation of running out in times of stress. Yes, offloading can take a bit of time - to tape. A better solution is to offload to DASD first, then have SMS archive.
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gbaddeley
PostPosted: Thu Feb 23, 2017 3:44 pm Post subject: Re: logging Reply with quote

Jedi

Joined: 25 Mar 2003
Posts: 2056
Location: Melbourne, Australia

bruce2359 wrote:
Planning for log size is well-documented. Part of the planning is having the appropriate (maximum) log extents in anticipation of running out in times of stress. Yes, offloading can take a bit of time - to tape. A better solution is to offload to DASD first, then have SMS archive.

Time of stress can be a badly behaved app that has long running UOWs (more than a few minutes).
Back in the old MVS days we had cases of MQ running out of logs, and hanging all UOWs, because of a broken tape drive allocated to an archive offload. Changing to DASD offload fixed that.
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Glenn
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exerk
PostPosted: Fri Feb 24, 2017 12:25 am Post subject: Reply with quote

Jedi Council

Joined: 02 Nov 2006
Posts: 6115

Doesn't everywhere use VTS these days?
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