database replication server is not running or running  on  other
  node

  Explanation:  The database replication  server  process  is  not
  running  on  the  standby  node  specified,  or  has  abnormally
  terminated.  There may also be a problem with the  mailbox  used
  to communicate with the database replication server.

  User Action:  Check the system to determine whether or  not  the
  database  replication server process is actually running on your
  system.  Check the use of cluster aliases,  as  the  replication
  connection  may  have  been  attempted  on  another  node of the
  designated cluster.  If the database replication server  process
  does  not appear to be running, have your database administrator
  start the replication server, and try again.   If  the  database
  replication  server process appears to be running properly, then
  the problem  may  be  related  to  the  mailbox  by  which  user
  processes communicate with the replication server process.  Make
  sure the "server name" specified for both the live  and  standby
  databases  logical  are unique and identical.  On VMS platforms,
  the "server name" is used to create a logical of the  same  name
  that  resides  in  a logical name table accessible to all users,
  typically  the  LNM$PERMANENT_MAILBOX  name   table.    If   the
  replication  server  process  abnormally  terminated, a bugcheck
  dump will normally be produced.  Search the bugcheck dump for  a
  string   of  five  asterisks  (*****)  using  the  SEARCH/WINDOW
  command.  You will see a line with a  format  similar  to  this:
  *****  Exception  at  <address>  :   <database  module  name>  +
  <offset> %facility-severity-text,  <error  text>  The  exception
  line will be followed by one or more additional errors that will
  help you to determine what caused the replication server process
  to  fail.   Typically,  the  problem  is  caused by insufficient
  quotas or system  resources.   However,  other  possible  causes
  include misdefined or undefined filename logicals.  Depending on
  the cause of the problem, take the appropriate action.   If  you
  are  uncertain  of  what  to  do,  contact  your  Oracle support
  representative for assistance.