Thanks Chuck,

I am using a 64-bit versions of the OS and JVM and I was confusing
virtual memory with RAM.

I have 8 GB of RAM and a 80 GB disc.

The commands -Xms3g -Xmx3g will set the min/max heap to 3 GB,please how
do I set the RAM for each instance of Tomcat5.5 to 2 GB

Regards

Peter
>> From: Peter Sparkes [mailto:peter@(protected)]
>> Subject: Memory usage with multiple instances of tomcat
>>
>> 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3
>> instance use 6 GB between them ?
>> 2. or do they potentially share they same memory?
>>  
>
> Don't confuse virtual memory with RAM. The heap allocations are
> virtual, so there is no physical relationship with the amount of RAM you
> have. (There are performance considerations, of course, in that if you
> significantly oversubscribe RAM, you may suffer from excessive paging.)
>
> One thing you've failed to mention is whether you're using 32- or 64-bit
> versions of the OS and JVM. If 32-bit, then process virtual space is
> typically limited to 2 GB, and the heap, code, and supporting libraries
> must fit within that - you won't be able to allocate all 2 GB to the
> heap. If you're running a 64-bit environment, the sky's the limit
> (almost), and you could make each heap 256 GB, even with only 8 GB of
> RAM (not recommended, due to aforementioned paging concerns).
>
> Since each Tomcat runs as a separate process, there is no active sharing
> of either heap or code across instances. However, if you're running a
> client version of a current HotSpot JVM, there is some sharing of loaded
> classes in the PermGen (other than static fields), primarily to reduce
> startup time. You can see the shared amount in the Memory tab of
> JConsole.
>
> There is not currently any sharing in the server version of the HotSpot
> JVM.
>
> - Chuck
>
>
> THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
> MATERIAL and is thus for use only by the intended recipient. If you
> received this in error, please contact the sender and delete the e-mail
> and its attachments from all computers.
>
> ---------------------------------------------------------------------
> To start a new topic, e-mail: users@(protected)
> To unsubscribe, e-mail: users-unsubscribe@(protected)
> For additional commands, e-mail: users-help@(protected)
>
>
>
>  


---------------------------------------------------------------------
To start a new topic, e-mail: users@(protected)
To unsubscribe, e-mail: users-unsubscribe@(protected)
For additional commands, e-mail: users-help@(protected)