1. 檢視 tnsnames.ora中條目 ：

bys3_dblk =

  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = bys3.bys.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = bys3)
    )
  )
/etc/hosts中不寫bys3.bys.com與IP的對應，也無法通過DNS得到bys3.bys.com的IP。

2.建立資料鏈並使用---

[email protected] bysrac1>create database link bys3_db connect to test9 identified by test9 using 'bys3_dblk';
Database link created.

此時使用DBLINK:  執行了很長時間，報錯：ORA-12545:Connect failed because target host or object does not exist
21:42:57 [email protected] bysrac1>select * from [email protected]_DB;
select * from [email protected]_DB
                    *
ERROR at line 1:
ORA-12545: Connect failed because target host or object does not exist
Elapsed: 00:02:40.25
###########3

3.檢視日誌中報錯資訊：

[[email protected] ~]$ cat alert_bysrac1.log
建立和使用資料鏈時會有類似如下報錯日誌：  --擷取部分
Sat Dec 28 21:41:29 2013
***********************************************************************
Fatal NI connect error 12545, connecting to:
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=racdg)(PORT=1521))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=racdg)(CID=(PROGRAM=oracle)(HOST=bysrac1.bys.com)(USER=oracle))))

  VERSION INFORMATION:
        TNS for Linux: Version 11.2.0.1.0 - Production
        TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.1.0 - Production
  Time: 28-DEC-2013 21:41:29
  Tracing not turned on.
  Tns error struct:
    ns main err code: 12545
    
TNS-12545: Connect failed because target host or object does not exist
    ns secondary err code: 12560
    nt main err code: 515
    
TNS-00515: Connect failed because target host or object does not exist
    nt secondary err code: 110
    nt OS err code: 0
###########

4.解決方法：

/etc/hosts中增加相應條目：

192.168.1.211   bys3.bys.com    bys3
ping bys3.bys.com   測試正常。

[email protected] bysrac1>select * from [email protected]_db;
AA
----------
dblink-ok    ---此時重新登陸資料庫,使用資料鏈正常：