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From Subir Sengupta <su...@walmart.com>
Subject RE: Tomcat oddities
Date Wed, 08 Jan 2003 23:51:00 GMT
Issue One:
If Tomcat used up all your memory, you would see OutOfMemory exceptions
being thrown, not a freeze.  Do you see these?  Everything will stop *while*
GC is occurring (not until GC occurs).  

Have you tried increasing the amount of memory allocated to Java?  Use the
-Xms and -Xmx flags to set memory allocations.  However, if you do have a
memory leak, increasing the memory will simply increase the intervals
between freezes.

-----Original Message-----
From: Michael Molloy [mailto:mmolloy@ncycles.com]
Sent: Wednesday, January 08, 2003 1:55 PM
To: Tomcat Users List
Subject: Tomcat oddities


My company is in the deployment stage of a project that uses tomcat to 
serve information from an oracle database to about 25 people. When the 
app goes live, there will be about 150 people connected at any one 
time. Tomcat 4.1.12 is running behind Apache on Windows 2000 on a 
single cpu box, and Oracle is running on a separate Windows 2000 2-way 
box. (Windows was the client decision, not ours.)

Issue One
We're seeing two serious issues, the first of which happens about once 
a day, sometimes more. When there are several users on the system, 
maybe up to 15, there is a freeze during which no one can get any 
responses back from Tomcat. This period usually lasts from 5 to 15 
minutes, after which the system returns to normal and everything zips 
along.

We've tuned queries, so we don't think that is the problem. There may 
still be a rogue query out there causing problems, but we think it's 
unlikely. Besides, I don't know why that would stop everyone, which is 
what's happening.

Another possibility that we've discussed is that tomcat is simply using 
all of the memory and everything basically stops until GC occurs. This 
seems the most likely to me, but I wanted to ask the group. I don't 
know what the page file size is, nor do we have access to the server so 
we can't check task manager.

Can anyone think of any other possibilities?

Issue Two
We've had two reports where a user has had data from an old session 
show up in his/her current session. For example, I wrote a class that 
stores information from 14 different JSPs. The object is put into the 
user's session. In these two occasions, the user entered a new record 
using these screens & saved the data to the database. The user took an 
hour lunch break, which would have been long enough to timeout (set at 
20 minutes), returned, and queried a different record. Some of the data 
from the previous record showed up in the holder class in his/her 
current session and was saved to the database.

Any idea what that could be? The only thing I can think of is that IE 
is doing some data caching & mixing things up a bit.

Any suggestions will be greatly appreciated. We really need to get this 
figured out quickly.

Thanks
--Michael Molloy


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