> We have multiple instances of JBoss running on one Linux box.
> Some JBoss instance occasionally resulted in the error. However,
> other instances of JBoss seem running without error. So, I don't
> think any of the items above is a cause of the error.

Please check your network settings. Can it be that you limited the number of
sockets that can be opened to the server?

> We can recover from the error by shutting down and restarting
> the JBoss instance in error(no need to shutdown/restart Firebird SS).
> This might suggest that something in JBoss connection management
> is wrong.
>
> We will appreciate any help/suggestions.

The error happens when JayBird tries to open new connection (seee the
GDS_Impl.connect method). So, that means either:

a) JBoss pool tries to increase the number of active connections in pool;

b) it tries to recover from the connection failure between transactions and
tries to reopen the connection.

Sorry, but it is either Java issue or your network configuration issue (at
least that's what I think it is). Or maybe Firebird SS does not want to
accept the connection, but I doubt that.

Roman