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.