unknown user "<str>"

  Explanation:  An attempt was made to access information  with  a
  user  name unknown to the database (for example, sending mail to
  the monitor or attempting to execute a database recovery process
  (DBR))  or to access information with a user name unknown to the
  operating system (for example, no record in the UAF file).

  User Action:  Make sure the user name is spelled  correctly  and
  has  been  properly  identified  to  either  the database or the
  operating system.  Do not attempt to run DBR from DCL;  this  is
  not  allowed,  because  the  system  will  automatically  manage
  database recovery.  Be sure the monitor user name  is  correctly
  specified.