Installed classes can reference other classes in the same JAR file and classes previously installed in the same database, but they cannot reference classes in other databases.
If the classes in a JAR file do reference undefined classes, an error may result:
If an undefined class is referenced directly in SQL, it causes a syntax error for “undefined class.”
If an undefined class is referenced within a Java method that has been invoked, it throws a Java exception that may be caught in the invoked Java method or cause the general SQL exception described in “Exceptions in Java-SQL methods”.
The definition of a class can contain references to unsupported classes and methods as long as they are not actively referenced or invoked. Similarly, an installed class can contain a reference to a user-defined class that is not installed in the same database as long as the class is not instantiated or referenced.