SQL does not allow <str> on sorted streams

  Explanation:  You have used MODIFY or ERASE on  a  stream  whose
  record  selection  expression  contains a SORTED BY clause.  SQL
  does not permit its equivalent  of  MODIFY  (UPDATE)  and  ERASE
  (DELETE)  to  operate on ordered streams as these are considered
  read only.

  User Action:  Rewrite your code so it does not attempt to modify
  or erase from these relations.