SQL> connect sys/******@&db_alias1 as sysdba
ERROR:
ORA-28547: connection to server failed, probable Oracle Net admin error 

SQL> startup nomount pfile="e:\oracle\product\10.2.0\db_1\database\init&db_alias1..ora"
ORA-24324: service handle not initialized
ORA-01041: internal error. hostdef extension doesn't exist

EXTPROC_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
    )
    (CONNECT_DATA =
      (SID = PLSExtProc)
      (PRESENTATION = RO)
    )
  )

DB56.WORLD =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = sestows146)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = sestows146)(PORT = 1526))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = DB56)
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = E:\oracle\product\10.2.0\db_1)
      (PROGRAM = extproc)

	(GLOBAL_DBNAME = DB56)
      (ORACLE_HOME = E:\oracle\product\10.2.0\db_1)
      (SID_NAME = DB56)
    )
  )

SQLNET.AUTHENTICATION_SERVICES = (NTS)
NAMES.DIRECTORY_PATH = (TNSNAMES)
NAMES.DEFAULT_DOMAIN = World

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = sestows146.prg-dc.dhl.com)(PORT = 1521))
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = E:\oracle\product\10.2.0\db_1)
      (PROGRAM = extproc)
    )
     (SID_DESC = 
      (SID_NAME = DB56)
      (ORACLE_HOME = E:\oracle\product\10.2.0\db_1)
      (SERVICE_NAME = DB56)
     )
  )