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James,
On 3/30/16 8:01 PM, James H. H. Lampert wrote:
> Earlier this week, we noticed that the JVM job (QP0ZPWT) assocated
> with the CATALINA job of a Tomcat server runs at Priority 6. This
> priority level puts it ahead of everything but the operating system
> itself.
>
> This morning, a response to a query on the Java forum at
> Midrange.com pointed me to this excerpt from catalina.sh:
>
>> if $os400; then # Set job priority to standard for interactive
>> (interactive - 6) by using # the interactive priority - 6, the
>> helper threads that respond to requests # will be running at the
>> same priority as interactive jobs. COMMAND='chgjob
>> job('$JOBNAME') runpty(6)' system $COMMAND
>>
>> # Enable multi threading export QIBM_MULTI_THREADED=Y fi
>
> This seems to be based on a misconception: run priority is a value
> from 0 to 99, with lower numbers denoting greater importantce. 0 is
> reserved for the operating system itself, 1-15 typically also used
> for the operating system itself, 20 used for most interactive jobs,
> 50 and up used for most batch jobs (including server jobs).
>
> Note: interactive jobs -- people signed on to physical terminals,
> or to terminal emulators -- typically run at priority 20. NOT
> priority 6.
>
> By setting Tomcat's JVM job at priority 6, we are not only putting
> it ahead of interactive jobs, but also ahead of all but the most
> important system jobs.
>
> Is there a reason for this? Or was it a simple misunderstanding of
> how priority works on AS/400s?
Unfortunately, the commit log shows Rémy committing that back in 2006
in r421604 where a bunch of files were added to the Tomcat 6 branch:
http://svn.apache.org/viewvc?view=revision&revision=421604
It looks like the actual contents of those files pre-dates Rémy's
commit, and I'm not sure how to track them back further... I can't
seem to find the original startup scripts from the 5.5.x branch just
by looking through viewvc. I'd have to checkout the whole project to
have a look.
I don't see any particular reason not to change this from priority 6
to priority 20. If you've got a (publicly-available) reference for
AS/400 that lists the appropriate priorities of different kinds of
jobs, I can change the priority there and reference that page for
interested parties.
- -chris
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