Double-booting system behavior prevents two instances of itself from booting the same database by using a file called db.lck inside the database directory.

If a second instance of attempts to boot an already running database, the following error messages appear:

ERROR XJ040: Failed to start database 'firstdb', see the next exception for details. ERROR XSDB6: Another instance of Derby may have already booted the database /home/myself/DERBYTUTOR/firstdb.

In addition, a stack trace appears in the derby.log file.

If you need to access a single database from more than one Java Virtual Machine (JVM), you will need to put a server solution in place. You can allow applications from multiple JVMs that need to access that database to connect to the server. The Network Server is provided as a server solution. For basic information on starting and using the Network Server, see . See the for more information on the Network Server.