RE: QDBSRVxx Job Hogging the CPU

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

Walden,

I have been investigating this problem and have some further information.  Your 
comments are 
not accurate.  Here is the truth:

The QDBSRV01 job does not determine the state of the access paths.  It is just 
an event handler 
and receives events indicating that an access path is invalid.  These events 
are sent from 
other processes.  

You are correct when you state that QDBSRV01 builds the EDTRDBAP panel 
information and that it 
passes the rebuild of the access path to one of the other QDBSRVnn jobs.

The events indicating an invalid access path come from a number of sources but 
in the example 
case are raised by the restore code (well actually lower-level LIC database 
code).  It is this 
code which checks for valid access paths and if it finds an invalid access path 
it sends an 
event to QDBSRV01 for each invalid access path.

What you see when QDBSRV01 sucks the life from the CPU is really the event 
handler code having 
a hard time because there are too many invalid indices.  (Your earlier comment 
about 50,000 
indices being a case in point.)

There are two solutions to this problem:
        1)  IBM rewrite the event handler code so it works better
        2)  Save the access paths and therefore reduce the number of events 
sent to QDBSRV01.

There is a caveat however.  The Backup and Recovery Guide describes some 
convoluted cases where 
an access path will be marked as invalid even if it was saved.  In these cases 
the QDBSRV01 
event handler will still get invoked although it may not get invoked as often 
as if you had not 
saved access paths.

Thanks for explaining the event handler problem should go to a friend of mine 
in Rochester.

Regards,
Simon Coulter.

//----------------------------------------------------------
// FlyByNight Software         AS/400 Technical Specialists
// Phone: +61 3 9419 0175      Mobile: +61 3 0411 091 400
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//--- forwarded letter -------------------------------------------------------
> Date: Mon, 02 Feb 98 08:48:30 -0500
> From: "Walden Leverich" <walden@techsoftinc.com>
> To: MIDRANGE-L@midrange.com
> Reply-To: MIDRANGE-L@midrange.com
> Subject: RE: QDBSRVxx Job Hogging the CPU
> Importance: Normal

> 
> Simon,
> 
> Sorry, but his won't help. The offending job is the job that determines if
> there is a saved access path and if so, if it is still valid. This job is
> the job that put the logicals on the EDTRBDAP screen. The actual rebuilds,
> if needed, occur at priority 52 so there is no (little) performance hit from
> the rebuild.
> 
> However, without regard to this problem, I agree that all saves (unless you
> have a REALLY good reason not to) should be done with save access paths
> (*yes).
> 
> -Walden
> 
> 

 

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