> And this connection pool is then used by JDBC data source. I guess - the only option is to change org.firebirdsql.pool.sun.AppServerConnectionPoolDataSource but what other value can I use - I guess, it can be the same as on other J2EE server like JBoss (it should have JDBC data source and connection pool as well).

If you do not need XA transactions, you can use the configuration with
JDBC driver. The connection pooling should be provided out of the box by
the Sun Application Server (sorry, I did not use it for a long time, but
there must be some docs how to configure connection pool with JDBC driver).

If you need XA transactions, there is no other way to use something
different than AppServerConnectionPoolDataSource. And I need a
reproducable test case (e.g. Server: EJB + config, client: JUnit) that
would reproduce the issue.

Roman