Cause: In a SQL statement, a reference
was made to an out-of-scope database object. The referenced object might be
misspelled, or the reference might be mixed, as in the following example:
CURSOR c1 IS SELECT dept.dname FROM emp;
Action: Check the spelling of all
database objects in the SQL statement, and make sure all references are to
objects within the current scope.

Relared Errors:
PLS-00328: A
subprogram body must be defined for the forward declaration of
string.
PLS-00329:
schema-level type has illegal reference to string
PLS-00330:
invalid use of type name or subtype name
PLS-00331:
illegal reference to string
PLS-00332:
string is not a valid prefix for a qualified name
PLS-00333:
string must match an object-table alias in this
context
PLS-00334:
string matches table or view without an alias
PLS-00335: a
package name conflicts with an existing object
PLS-00336:
non-object-table string illegal in this context
PLS-00337:
string matches too many object table aliases