• 1.  Linear log management

    Posted Fri July 02, 2021 11:49 AM
    In the very distant past, I had learned a number of things about how linear logs work.
    In particular, that the QM would "occasionally" do rdcmqimg's when it saw fit, in order to release the oldest logs.
    Sometimes a manual rcdmqimg had to be done to force the release of the logs.

    I understood that leaving the IMGSCHED parameter to manual would keep this behaviour. But obviously this is not the case.

    So either a QM has never done rcdmqimg by itself (and I'm ashamed to have thought so!), or this has changed since 9.0.2 and the possibility to have logs in automatic management.

    Thank you in advance for your insights.

    Luc-Michel Demey

  • 2.  RE: Linear log management

    Posted Mon July 05, 2021 03:54 AM
    hi Luc-Michel,
    all change in 9.0.2 ( from infocenter: "From IBM MQ 9.0.2 you have the option to use automatic management of linear log extents no longer required for recovery.")

    I would now recommend linear logging to even the simplest of my customers since this change :-) 

    best regards,

    John Hawkins
    Integration Consultant

  • 3.  RE: Linear log management

    Posted Mon July 05, 2021 04:07 AM
    Hi Luc-Michel,

    Prior to automatic log image recording (v9.0.2) it was necessary to manually record the images with linear logs. You probably got confused between image recording and log checkpointing (which is done automatically when the queue manager decides to).

    As John said, I've got customers using linear logs now where in the past they would have used circular logs to avoid the management issues with manually (or even scripted) image recording and deleting the log tail.

    All the best,

    Neil Casey.

    Neil Casey
    Senior Consultant
    Syntegrity Solutions
    Melbourne, Victoria
    IBM Champion (Cloud) 2019-21

  • 4.  RE: Linear log management

    Posted Wed July 07, 2021 09:25 AM
    Thank you Neil for these clarifications.

    The terrible thing is that for more than 10 years (20?) I was convinced of the contrary!
    At the time, the documentation on this point was a little ... light.
    And as I systematically installed the linear log purging tools (SupportPacs MS0L, M073, or MS62) with a forced rcdmqmimg, I could never notice that the image recording was not done automatically.

    I will update my installation checklist.

    Luc-Michel Demey