Java startup - how to change the DB2 port

We moved the DB2 (on AIX) database to a different database server and changed to a new port to avoid a conflict. The ABAP stack starts up ok, but the java stack fails with an error indicating that the old port (5912) is still being used.

The configtool cannot connect for the same reason.

Does anyone know how to alter the DB2 port for the Java stack?