tnsname.ora的介绍

设定tnsnames.ora
###orcl只是名字而已可以更改，tnsping  orcl和 sqlplus  sys/dab@orcl时候可以用
ORCL =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.29)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = orcl)  #这个是对方的listen里面的 sid或者服务名
    )
  )

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

A服务器：create public database link A_TO_B（联结的名字） connect to tmp identified by tmp using 'TNSA_B'（tnsnames里面的名字）;
         #create public database link orcl.shanghai　using　'shanghai';
select * from haha@A_TO_B(联结的名字);