Hi James,

I didn't see any responses to your mail. You can google for various
profilers and monitors, but the one I've used on the AS/400 is IBM iDoctor:

https://www-912.ibm.com/i_dir/idoctor.nsf

It has ( or had ) both free and pay portions. That same page has a link
other debugging tools at the bottom.

Keep in mind that there are at least three areas where problems can
arise: an individual application, Tomcat, the JVM. Add to that multiple
users on the AS/400, so the problem could be caused or exacerbated by other
unrelated programs, pool allocations, etc.

In my own case, the classic JVM was running asynchronous garbage
collections that didn't finish before another was requested. Inadequate
memory and thread contention eventually caused the app ( WebSphere server
and associated web apps ) to freeze with long delays ( sometimes hours ) before the gc runs completed. This was even after various termination attempts.

The problem was eventually "resolved" by "found" additional memory
allocated to the subsystem. I was not happy that expensive AS/400 memory
was dedicated to WebSphere when many other applications and users were on
the machine, but the company "gurus" were AIX guys who didn't understand how
the AS/400 works.

Even so, I think my solution eventually would have been queueing up
report requests and notifying users when the report was available. I
suspect other web apps were less than efficient in database access and
paging, but I often saw the memory jump when multiple reports ( which are by
nature batch processes, even if the trend is to run them interactively on
the web ) were requested simultaneously.

So, the causes may be less than obvious, especially if you only see it
on one client.

Also, high CPU is not necessarily bad; depends on whether cycles are
effectively being stolen from other applications.

HTH somewhat.


Joe Sam

Joe Sam Shirah - www.conceptgo.com (904) 302-6870
conceptGO - Consulting/Development/Outsourcing
Java Filter Forum: www.ibm.com/developerworks/java/
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-----Original Message----- From: James Lampert
Sent: Wednesday, June 20, 2012 11:45 AM
To: Java Programming on and around the IBM i
Subject: High CPU usage in Tomcat 7

We just had a report of some honking high CPU usage from one of our
customer Tomcat installations.

We terminated and restarted the CATALINA job; The only screen shot I
have of a WRKACTJOB while the problem was occurring shows:
CATALINA BCH .0 CMD-QSH TIMW
QP0ZSPWT BCI 112.2 JVM-org.apache TIMW

I did a Google search on "tomcat 7 high cpu usage"; what I got back
suggests profilers and thread dumps, to find the offending thread. How
would I do this on an AS/400?

--
JHHL
--

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