Is there any way to keep Oracle SQL Developer from closing my DB connections, or to increase the timeout? Sometimes during a long-running query SQL Dev will just close the conne
Also sounds like a firewall problem to me.
You may have some luck with setting EXPIRE_TIME parameter in the server's SQLNET.ORA file. From the documentation:
Use parameter SQLNET.EXPIRE_TIME to specify a the time interval, in minutes, to send a probe to verify that client/server connections are active. Setting a value greater than 0 ensures that connections are not left open indefinitely, due to an abnormal client termination. If the probe finds a terminated connection, or a connection that is no longer in use, it returns an error, causing the server process to exit. This parameter is primarily intended for the database server, which typically handles multiple connections at any one time.
10g Documentation on EXPIRE_TIME