This
is digging back into my memory somewhat and so I hope I have it right. The MQ
logs actualy have two types, at least, of information in
them.
Type
one are the records necessary for recovering messages and Unit of Work
information, these exist in both circular and linear logs and are used for
"restart recovery".
Type
two are the records necessary to recover the definitions of your various MQ
objects and exist in linear logs only. They exist for what is called "media
recovery" i.e. a hard-disk failure where the MQ object definitions are
lost.
Object
definitions are recorded in the logs from when you first created your queue
manager and every time you define a new MQ object e.g. a queue or alter the
definitons of an exisitng object.
Hence
the media recovery pointer will point to your first log. When you issue the
rcdmqimg command with -t all \* option you are telling MQ to write all the
objects definitions out again. This has the effect of moving the "media
recovery" pointer to the latest log and hence the old logs become eligible to be
released providing of course that they are not require for "restart recovery" as
well because of a long running unit of work.
This
is why your ../WebsphereMQ/log directory should be defined on a different
physical volume from the rest of the MQ related directories. It also helps from
a performance point of view.
Regards
Tim
A
-----Original Message-----
From: John Elgie [mailto:[EMAIL PROTECTED]
Sent: Tuesday, 29 June 2004 10:00 AM
To: [EMAIL PROTECTED]
Subject: Why running rcdmqimg would free up linear log?I am running a 5.3.0.5 qmgr on aix. We had a qmgr with linear logs that was not releasing an old log that it needed for media recovery.
There were no outstanding transactions from dspmqtrn.
Running rcdmqimg -m qmgr -t all \* immediately released the old log for media recovery. Support docs. specifically say the rcdmqimg does NOT do log checkpointing. Is this a co-incidence? or is there another reason?
John Elgie
8-3777 Kingsway, Burnaby, V5H 3Z7
Desk: (604)432-4675
Cell: (604)315-7940
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