今天使用SQL Developer連接一臺測試服務器數據庫（ORACLE 11g）時，遇到了“ORA-12514, TNS:listener does not currently know of service requested in connect descriptor”錯誤，具體提示如下所示：

執行請求的操作時遇到錯誤:

Listener refused the connection with the following error:

ORA-12514, TNS:listener does not currently know of service requested in connect descriptor

供應商代碼 12514

Step 1： 首先檢查客戶端的tnsnames.ora里面的host、port、service_name等是否正確

myvm =

 (DESCRIPTION =

 (ADDRESS_LIST =

 (ADDRESS = (PROTOCOL = TCP)(HOST = 10.20.57.15)(PORT = 1521))

 )

 (CONNECT_DATA =

 (SERVER = SHARED)

 (SERVICE_NAME = gsp.localdomain)

 )

 )

逐一仔細檢查過后發現這些配置都是正確的。 其實前幾天還是正常來的。測試服務器和tnsnames.ora都沒有改動過。所以我們繼續后面排查。

Step 2：檢查確認數據庫實例是否啟動。

SQL> select status from v$instance;

STATUS

------------

OPEN

SQL> 

如上所示，數據庫實例正常，并沒有關閉。當數據庫實例異常關閉，也會出現ORA-12514錯誤，如下所示（如果我關閉一數據庫實例，然后使用SQL*Plus測試連接數據庫就會遇到這個錯誤）：

C:\Users>sqlplus system/123456@mydb

SQL*Plus: Release 11.2.0.1.0 Production on 星期三 4月 12 11:56

Copyright (c) 1982, 2010, Oracle. All rights reserved.

ERROR:

ORA-12514: TNS: 監聽程序當前無法識別連接描述符中請求的服務

Step 3：檢查網絡是否正常，tnsping能否ping通

如下所示，ping 和tnsping 均都正常

監聽服務也正常，沒有問題

[oracle@DB-Server admin]$ lsnrctl status

LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 12-APR-2017 10:36:40

Copyright (c) 1991, 2009, Oracle. All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))

STATUS of the LISTENER

------------------------

Alias LISTENER

Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production

StartDate 12-APR-2017 10:31:20

Uptime 0 days 0 hr. 5 min. 20 sec

Trace Level off

Security ON: Local OS Authentication

SNMP OFF

Listener ParameterFile /u01/app/oracle/product/11.1.0/dbhome_1/network/admin/listener.ora

Listener Log File /u01/app/oracle/diag/tnslsnr/DB-Server/listener/alert/log.xml

Listening Endpoints Summary...

 (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))

 (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=DB-Server.localdomain)(PORT=1521)))

The listener supports no services

The command completed successfully

Step 4：檢查$ORACLE_BASE/diag/tnslsnr/DB-Server/listener/alert下的日志，發現host_addr為10.20.34.76，實際IP地址不是這個。因為監聽文件里面我使用的hostname DB-Server.localdomain，所以趕緊檢查/etc/hosts的配置

[root@DB-Server ~]# ifconfig

eth0 Link encap:Ethernet HWaddr B0:83:FE:55:32:E5 

 inet addr:10.20.57.15 Bcast:10.20.57.255 Mask:255.255.255.0

 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

 RX packets:2363981 errors:0 dropped:0 overruns:0 frame:0

 TX packets:180048 errors:0 dropped:0 overruns:0 carrier:0

 collisions:0 txqueuelen:1000 

 RX bytes:225925147 (215.4 MiB) TX bytes:14349633 (13.6 MiB)

 Interrupt:233 Base address:0x4000 

lo Link encap:Local Loopback 

 inet addr:127.0.0.1 Mask:255.0.0.0

 UP LOOPBACK RUNNING MTU:16436 Metric:1

 RX packets:3692 errors:0 dropped:0 overruns:0 frame:0

 TX packets:3692 errors:0 dropped:0 overruns:0 carrier:0

 collisions:0 txqueuelen:0 

 RX bytes:2982961 (2.8 MiB) TX bytes:2982961 (2.8 MiB)

[root@DB-Server ~]# more /etc/hosts

# Do not remove the following line, or various programs

# that require network functionality will fail.

10.20.34.76 DB-Server.localdomain DB-Server

127.0.0.1 localhost.localdomain localhost

::1 localhost6.localdomain6 localhost6

[root@DB-Server ~]# 

果然發現/etc/hosts下配置為10.20.34.76， 具體原因是因為IT部門調換辦公室，從三樓撤到二樓，將這臺PC搬下來后，服務器IP地址變化了，修改/etc/hosts，然后重啟監聽服務，問題解決。

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