Re: JDBC HIGH CPU and Restart Issue

["Joe Sam Shirah" <joe_sam@xxxxxxxxxxxxx>]

   Hi Thorbjørn,

   I'll own up that I haven't used the J9 JVM's so far, so the rest is just
my understanding.  Real world users, please add your experiences.  I'll soon
be starting on a client project (that may go commercial subscription -- let
me know if your CFO wants to rein in cash flow and receivables) with what I
would describe as a 4-tier system. The 32 bit jvm makes a lot of sense for
the 4th tier, and I'll be happy to share any AS/400-centric issues as I go.

   The J9 JVM is much more similar to other JVM's in terms of tuning and
operating characteristics.  For technical information, google:

   "Holly Cummins" ibm jvm

Dr. Cummins adds a whole new meaning to "blue".  BTW, this is pretty
important reading because the classic JVM is due to go away.

   The main thing, IMO, for midrangers (and mainframers) to keep in mind is
that most mainstream JVM and grabage collection discussions pretty much
assume a dedicated machine for server apps.  On the AS/400, I'm always very
sensitive to the more common scenarion of many users and jobs going on, and
the need for balanced, consistent operations.  That's one of several reasons
I prefer to run JEE and web apps on a separate platform; I can have a
relatively cheap dedicated box and access the AS/400 for what I need.

   The need for that type of knowledge and understanding won't go away with
J9.  I would be less concerned about paging with J9, although in-memory is
always going to be faster.  But, in the real world, no paging is often not
going to be a realistic option, and other systems cope reasonably well with
paging.  Again, IMO, the big issue in the future is going to be properly
handling and writing parallel code to deal with lower powered multi-core
systems.

   But enough opinion.  What do the real worlders have to say?


                                                        Joe Sam

Joe Sam Shirah -        http://www.conceptgo.com
conceptGO       -        Consulting/Development/Outsourcing
Java Filter Forum:       http://www.ibm.com/developerworks/java/
Just the JDBC FAQs: http://www.jguru.com/faq/JDBC
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Que Java400?            http://www.jguru.com/faq/Java400

----- Original Message ----- 
From: "Thorbjoern Ravn Andersen" <ravn@xxxxxxxxxx>
To: "Java Programming on and around the iSeries / AS400"
<java400-l@xxxxxxxxxxxx>
Sent: Friday, May 07, 2010 1:05 PM
Subject: Re: JDBC HIGH CPU and Restart Issue


Den 07/05/10 10.40, Joe Sam Shirah skrev:
>      With the classic JVM, a major goal is to avoid disk paging
> altogether.
> That's mostly due to asynchronous gc, but also performance in general.
I can only agree with the paging.  Do you have similar advice to share
for the J9 JVM?