Re: (Java) Synchronizing multiple app servers through Oracle

On Dec 19, 12:05 pm, chrism..._at_gmail.com wrote:
> > > Typically the lock will last less than one second.
>
>
>
> > I'd say that's pretty long. How often will you - pardon, your
> > application - acquire the lock and what's the general load pattern of
> > the application?
>
> Yes, it's not that short of a period of time, but unfortunately,
> that's how long it takes to grab unique records. Right now we have 2
> app servers each hitting the database once per second and acquiring a
> lock. However, the number of app servers could grow to 10 or more. I
> wrote a multi-threaded test to simulate multiple servers, and found
> that Oracle appears to have a problem when more than 10 locks are
> acquired at the same time. It seems to just give up and wait for the
> timeout once too many have been acquired. Is there a setting in
> Oracle to handle more simultaneous locks?

It kind of depends what exactly is going on. Metalink Note:15476.1 is a basic description of locks and how to see what is locked. Note: 402983.1 is a performance FAQ that includes how to check if the db is really hung. The Performance manual in the doc set describes how to check what is really being waited for. Views such as dba_lock and v $session_wait can really help, and don't discount some of the graphic tools available.

If you are not using the default locking methods, you need to understand what you are doing and how to use the instrumentation available to understand it. Once you understand the actual problem, you can fix it, if you haven't designed your strategy to be unfixable. Asking for a setting for more simultaneous locks - well, you might want to review the Concepts manual on locking, you may have some misconceptions.

Before you do any of that... when "oracle appears to have a problem..." are your cpu's going nuts? Do you see very high latch waits? What version and platform, exactly (10g isn't enough, we need something like 10.2.0.4), are you using? What locks are you aquiring?

jg

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