When referencing an identifier, you use a name that is either simple, qualified, remote, or both qualified and remote.

The simple name of an identifier is the name in its declaration. For example:

DECLARE
  a INTEGER;  -- Declaration
BEGIN
  a := 1;     -- Reference with simple name
END;
/

If an identifier is declared in a named PL/SQL unit, you can (and sometimes must) reference it with its qualified name. The syntax (called dot notation) is:

unit_name.simple_identifier_name

For example, if package p declares identifier a, you can reference the identifier with the qualified name p.a. The unit name also can (and sometimes must) be qualified. You must qualify an identifier when it is not visible (see "Scope and Visibility of Identifiers").

If the identifier names an object on a remote database, you must reference it with its remote name. The syntax is:

simple_identifier_name@link_to_remote_database

If the identifier is declared in a PL/SQL unit on a remote database, you must reference it with its qualified remote name. The syntax is:

unit_name.simple_identifier_name@link_to_remote_database

You can create synonyms for remote schema objects, but you cannot create synonyms for objects declared in PL/SQL subprograms or packages. To create a synonym, use the SQL statement CREATE SYNONYM, explained in Oracle Database SQL Language Reference.

For information about how PL/SQL resolves ambiguous names, see PL/SQL Name Resolution.