Cause: In a declaration, the name of a
variable or cursor is misspelled or the declaration makes a forward reference.
Forward references are not allowed in PL/SQL. A variable or cursor must be
declared before it is referenced it in other statements, including other
declarative statements. For example, the following declaration of dept_rec
raises this exception because it refers to a cursor not yet declared: DECLARE
dept_rec dept_cur%ROWTYPE; CURSOR dept_cur IS SELECT … …
Action: Check the spelling of all
identifiers in the declaration. If necessary, move the declaration so that it
makes no forward references.

Relared Errors:
PLS-00321:
expression `string` is inappropriate as the left hand side of an
assignmen
PLS-00322:
declaration of a constant `string` must contain an initialization
assignme
PLS-00323:
subprogram or cursor `string` is declared in a package specification
and m
PLS-00324:
cursor attribute may not be applied to non-cursor
`string`
PLS-00325:
non-integral numeric literal string is inappropriate in this
context
PLS-00326: IN
clause must contain same number of expressions as subquery
PLS-00327:
string is not in SQL scope here
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