DB1.UK, DB2.UK =
  (
    (ADDRESS = (PROTOCAL = TCP))
    (CONNECT_DATA = (SID = db1))
  )

DB1.EU, DB2.CH =
  (
    (ADDRESS = (PROTOCAL = TCP))
    (CONNECT_DATA = (SID = db1))
  )

DB3.UK =
  (
    (ADDRESS = (PROTOCAL = TCP))
    (CONNECT_DATA = (SID = db3))
  )

DB3.US =
  (
    (ADDRESS = (PROTOCAL = TCP))
    (CONNECT_DATA = (SID = db3))
  )

DB5.UK.US, DB5.US =
  (
    (ADDRESS = (PROTOCAL = TCP))
    (CONNECT_DATA = (SID = db5))
  )