Maximum Memory Issues

[Ed Gomolka <eg...@ausinfo.com>]

A few days ago, I posted an e-mail about the Java maximum memory
heap size.
(We have a client in the happy situation of having 4 Gigs on their servers,
and they
were frustrated about not being able to specify more than 2 Gigs in the -Xmx
option.
I got some good advice from the mailing list about how to set up multiple
instances of Tomcat.)

Now the client has further informed me that when they provide a maximum heap
value of more than 700 Megs,
Tomcat is unstable, and invariably crashes after a while.
They are running Tomcat 3.2b2 on a Sun Sparc machine using Solaris 7 (I
don't remember the machine model
number but they've only had it for a month, and it's one of the biggest
machines you can get).
They actually have more than one machine of this type (4, I believe), all of
which are exactly the
same.
The client is in another city, and therefore the communication is sometimes
a bit spotty, so I don't have more
detailed info on the nature of the crashes, but it seems to vary.
Unfortunately, our test machines
here only have 512 Megs of memory, so I can't duplicate the situation
either.

My question is:
Has anyone else experienced this?
Does anyone have an idea why this should be an issue?
Also, does anyone know of any stability/performance issues that were
resolved between 3.2b2 and 3.2b6?

If need be, I suppose that we could just have more Tomcat instances, but it
seems to me that this
shouldn't be necessary.
This site only has one servlet at the moment, but we have to have a servlet
to facilitate
our applet/server communication, and we anticipate very heavy site usage.
We're already getting
thousands of hits a day, and the client hasn't even started advertising.
We are keeping the memory below 700 Megs, but we have had the servers go
down a
couple of times already (I'm waiting to receive a Tomcat log file while I'm
writing this note).

I feel that in terms of performance tuning, we haven't even scratched the
surface, but I nevertheless
get a bit nervous when I hear about servers going down.

Despite the heavy traffic, the servlet usage is relatively light. A user may
stay on the site for
10-15 minutes, but they only need to access one servlet, at the end of their
session. This is done in order
to transmit data from an applet to the server, which can take about 20
seconds, but may take longer
because if the servers are occupied, they will be queued up behind other
users.
Due to this setup, we figured that we could get away with using Tomcat as
opposed to some other,
more industrial strength, servlet engine.
(Also, I'm a fan of open source, and I personally like the idea of using
something like Tomcat.)

This is probably all a bit vague, but if anyone has any suggestions or
opinions on what I
should be looking at to resolve this, I'd appreciate them.

Thanks in advance.

Ed
----------------------
Ed Gomolka
(egomolka@ausinfo.com)