Re: Checking a JVM for out-of-memory?

You can run out in two circumstances.
1) You've set the -Mx value in the java command line.
2) The JVM is running in a constrained storage pool.

The OS cares nothing about running out of allocated memory as set in -Mx. You'll get a Java-specific message about that.

I don't think there's anything you can do about running out of memory in a constrained storage pool. As David points out, the memory is just going to page out until the garbage collector starts to barf when it tries to clear memory that has to be paged in. It barfs but never quits; just goes slowly. I suppose you could try to constrain the disk storage for the job; then you'd get some kind of a message from the OS when the job exceeded the disk limit. I think there's a setting in the job description for setting the max storage for the job.

----- Original Message ----- From: "David Gibbs" <david@xxxxxxxxxxxx>
To: "Java Programming on and around the IBM i" <java400-l@xxxxxxxxxxxx>
Sent: Monday, March 24, 2014 1:39 PM
Subject: Re: Checking a JVM for out-of-memory?

On 3/24/2014 1:27 PM, James H. H. Lampert wrote:

Is there anything OS/400-specific for detecting an out-of-memory
condition on a JVM job?

I'm not 100% sure, but I don't think you can actually run out of memory with the IBM i JVM.

I think you can use so much memory that the job starts paging memory in & out at a rate that causes performance problems.

I could be wrong.

david

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