Cause: An attempt was made to make a
reference from a schema-level type to something other than a schema-level
type.
Action: Replace the illegal reference
and retry the operation.

Relared Errors:
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
PLS-00338:
unable to resolve string as a column or row
expression
PLS-00339:
string matches object-table without a REF or VALUE
modifier