ORA-24856
invalid use of TO_LOB operator
Cause
You can apply this function only to a LONG or LONG RAW column, in the select list of a subquery in an INSERT statement. Also, it is possible to use the TO_LOB function to convert a LONG column to a LOB column in the subquery of a CREATE TABLE ... AS SELECT statement, if you are not creating an INDEX organized table. TO_LOB function is not allowed within a PL/SQL package.
Action
Remove the TO_LOB operator. In the case the operator is in a PL/SQL package, use the TO_CLOB or TO_BLOB functions instead.