Check if a table is updatable by query user_updatable_columns : user_updatable_columns « System Tables Data Dictionary « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. System Tables Data Dictionary
3. user_updatable_columns

SQL>
SQL> select column_name
  2  ,      updatable, insertable, deletable
  3  from   user_updatable_columns
  4  where  table_name = 'EMPLOYEES';

no rows selected

SQL>
SQL>