A resource manager is closed by the resource adapter as a result of destroying the transactional resource. A transaction resource at the resource adapter level is comprised of two separate objects:
XAResource object that allows the transaction manager to
end the transaction association with the resource in use, and to coordinate the transaction completion process.
A connection object that allows the application to perform operations on the underlying resource (for example, JDBC operations on an RDBMS).
Once opened, the resource manager is kept open until the resource is explicitly released (closed). When the application invokes the connection’s
close method, the resource adapter invalidates the connection object reference that was held by the application, notifying the application server about the
close. The transaction manager needs to invoke the
XAResource.end method to dissociate the transaction from that connection.
close notification allows the application server to perform any necessary garbage collection and mark the physical XA connection as free for reuse, in the case of connection pooling.