When you reference identifiers, you can use simple, qualified, and remote names or qualified and remote names.
If you declare an identifier in a named PL unit, you can, and sometimes must, reference it by using its qualified name. Syntax:
unit_name.simple_identifier_name
For example, if you declare identifier c in the ob package, you can use the qualified name ob.c to reference the identifier. Unit names can, and sometimes must, be qualified as well. If an identifier is invisible, it must be qualified. For more information, see Scope and visibility of identifiers.
If you use an identifier to name an object on a remote database, you must reference the identifier with its remote name. Syntax:
simple_identifier_name@link_to_remote_database
If an identifier is declared in a PL unit on a remote database, you must reference the identifier with its qualified remote name. Syntax:
unit_name.simple_identifier_name@link_to_remote_database