ORA-28575: unable to open RPC connection to external procedure agent

One of the common Error with EXTPROC connection is ORA-28575 .
The Below article will suit for the server having 9i/10g or 9i/10g/11g installed .
In this case you will be having extproc for each Version running in different port and listener.


LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (PROTOCOL_STACK = (PRESENTATION = TTC)(SESSION = NS))
      (ADDRESS = (PROTOCOL = TCP)(HOST = <<HOST>>)(PORT = 1524))
      (ADDRESS = (PROTOCOL = IPC)(KEY = extproc_key_1))
    )
  )
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (PROGRAM = extproc)
      (SID_NAME = extproc1)
      (ORACLE_HOME = <<ORACLE9i_HOME>>)
      (ENVS='EXTPROC_DLLS=ANY')
    ) )
LISTENER_10g =

  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (PROTOCOL_STACK = (PRESENTATION = TTC)(SESSION = NS))
      (ADDRESS = (PROTOCOL = TCP) (HOST = <<HOST>>) (PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC) (KEY = extproc_key_2))
    )
  )
SID_LIST_LISTENER_10g =
  (SID_LIST =
    (SID_DESC =
      (PROGRAM = extproc)
      (SID_NAME = extproc2)
      (ORACLE_HOME = <<ORACLE_10g_HOME>>)
      (ENVS='EXTPROC_DLLS=ANY')
    )
  )

And while connecting to the extproc you will get the bleow error,

ORA-28575: unable to open RPC connection to external procedure agent

One of the solution to this error is ,

• Stop the listener
• Set the TNS_ADMIN pointing to the correct EXTPROC
• Start the listener

Testing EXTPROC : Metalink 47484.1