attempt to start replication for wrong master database

  Explanation:  An attempt has been made to start replication on a
  master  database whose standby database is already replicating a
  different master database.  The master root file name  does  not
  match  the  name  used when replication was first started on the
  standby database.  This could happen if you  copied  or  renamed
  the  master database root file, or if the file was created using
  a concealed logical device name and  that  logical  name  is  no
  longer defined.

  User Action:  Ensure that  the  specified  standby  database  is
  correct.  If so, ensure that replication on the standby database
  has been fully terminated; replication termination occassionally
  has  long-duration  shutdown processing to be performed.  If the
  master database rootfile had been moved, rename or copy the root
  file  back  to  its  original  name or location, or redefine the
  necessary concealed logical device name in  the  system  logical
  name table.