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  • 1.  Cause of CICS Sync point dispatch time attributed to DB2

    Posted Oct 30, 2020 03:49 PM
    Edited by Donna Domovic Oct 30, 2020 04:04 PM
    Hello,

    Have a strange one that has us banging our heads on.

    We've noticed that we periodically have times where we see the Sync point dispatch time in the CICS monitor (ie SYSVIEW) showing large values (5+ seconds).  Looking into it, the majority of this corresponds to large RMIDb2 times that aren't accounted for at the DB2 statement level.  From what we've seen, the CPU does not appear to be maxed out during these periods.

    We investigated this using various monitoring tools such as CA Sysview/Insight for DB2, BMC Apptune,, and SMF reports but don't see any place on the DB2 side that accounts for this.  All statements are executing quickly.

    As we've investigated this, we've also noticed that this appears to be isolated to 1 LPAR but not to a single CICS region, DB2 data sharing group, or application..  When it happens, it seems to impact all of them on that LPAR for the short period when it happens (less than 1 minute) which makes me lean towards it being something at the LPAR/system level rather than a DB2, CICS, or application problem.

    We are looking to see if we can find any pattern to when it happens and if there could be something running during that time that could account for this but so far have not had any luck despite different teams taking a look.  Given the wide community here, I was curious if anyone has ideas or has seen something like this.  If you have ideas on what we may be missing or what we might want to look at, I'm interested in those ideas as well.

    Thanks in advance for any information or ideas you provide.

    ------------------------------
    Donna Domovic 
    Exelon
    ------------------------------


  • 2.  RE: Cause of CICS Sync point dispatch time attributed to DB2

    Posted Oct 31, 2020 12:45 AM
    We recently had an occasion where it turned out the culprit was CICS system logging - or
    rather deleting old achived systems logs. Seems when the retained log count is reached,
    the system logger will delete the oldest archived log - before the switch takes place and the
    CICS sync happens.

    Someone decided to reduce the retained log count by many, many thousands.

    James Campbell


    On 30 Oct 2020 at 19:48, Donna Domovic via Internation wrote:

    > Hello,
    >
    > Have a strange one that has us banging our heads on.
    >
    > We've noticed that we periodically have times where we see the Sync point dispatch time in the CICS monitor (ie SYSVIEW) showing large values (5+ seconds). Looking into it, the majority of this corresponds to large RMIDb2 times that aren't accounted for at the DB2 statement level. From what we've seen, the CPU does not appear to be maxed out during these periods.
    >
    > We investigated this using various monitoring tools such as CA Sysview/Insight for DB2, BMC Apptune,, and SMF reports but don't see any place on the DB2 side that accounts for this. All statements are executing quickly.
    >
    > As we've investigated this, we've also noticed that this appears to be isolated to 1 LPAR but not to a single CICS region, DB2 data sharing group, or application.. When it happens, it seems to impact all of them on that LPAR for the short period when it happens (less than 1 minute) which makes me lean towards it being something at the LPAR/system level rather than a DB2, CICS, or application problem.
    >
    > We are looking to see if we can find any pattern to when it happens and if there could be something running during that time that could account for this but so far have not had any luck despite different teams taking a look. Given the wide community here, I was curious if anyone has ideas or has seen something like this. If you have ideas on what we may be missing or what we might want to look at, I'm interested in those ideas as well.
    >
    > Thanks in advance for any information or ideas you provide.
    >
    > ------------------------------
    > Donna Domovic


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  • 3.  RE: Cause of CICS Sync point dispatch time attributed to DB2

    Posted Nov 02, 2020 01:48 PM
    James,

    Thanks for replying and for the information.  Definitely something worth checking. 

    I've passed the information on to our CICS team to take a look.  We'll see what they find and if this is a match. 

    Thanks,

    ------------------------------
    Donna Domovic
    Exelon
    ------------------------------



  • 4.  RE: Cause of CICS Sync point dispatch time attributed to DB2

    Posted Oct 03, 2022 01:14 AM
    Hello,
    I am very interested to know if and how this issue was resolved,
    since we're having a similar problem at our site.
    thanks,
    Yaron Tal

    ------------------------------
    YaronTalFreelance
    ------------------------------



  • 5.  RE: Cause of CICS Sync point dispatch time attributed to DB2

    Posted Oct 11, 2022 07:48 AM
    Hi,

    Sorry for the delay responding to this.  We never actually tracked down the cause.  It did get better but we're not sure why.  We tend to think there was something else going on on the mainframe impacting this and leading to what we were seeing but haven't been able to find a definitive explanation.

    Sorry I don't have a better answer for you.

    Thanks,
    Donna Domovic

    ------------------------------
    Donna Domovic
    ------------------------------