This is because an IDE might try connecting to the database from two different
JVMs, whereas only a single JVM instance should connect to a database
at one time (multiple connections from the same JVM are allowed).
An "embedded application"
is one which runs in the same JVM as the application. Such an application
uses the embedded driver
(org.apache.derby.jdbc.EmbeddedDriver) and connection URL (jdbc:derby:databaseName).
If you use this driver name or connection URL from the IDE, when the IDE tries
to open a second connection to the same database with the embedded ,
the attempt fails. Two JVMs cannot connect to the same database in embedded
mode.