■ 江蘇 繆振龍

編者按：本文是筆者親歷的一次Oracle TNS連接超時(shí)引起的故障，雖然看似疑難，但最終發(fā)現(xiàn)是由于一個(gè)簡(jiǎn)單的配置文件錯(cuò)誤導(dǎo)致。

筆者最近準(zhǔn)備對(duì)一臺(tái)Oracle 10g數(shù)據(jù)庫(kù)進(jìn)行數(shù)據(jù)備份，采用exp方式全庫(kù)導(dǎo)出。但嘗試多次，一直提示如下錯(cuò)誤：

EXP-00056: ORACLE error 12170 encountered

ORA-12170: TNS:Connect timeout occurred

EXP-00000: Export terminated unsuccessfully

經(jīng)查閱相關(guān)資料得知，“EXP-00056”產(chǎn)生錯(cuò)誤的原因是“ORA-12170”。具體來(lái)說(shuō)是由于TNS連接超時(shí)導(dǎo)致。

TNS是Oracle Net的一部分，用來(lái)管理和配置Oracle數(shù)據(jù)庫(kù)和客戶端的連接工具，客戶端只有正確配置TNS相關(guān)文件才能訪問Oracle服務(wù)器。

故障分析

在日常維護(hù)中通常使用tnsping命令檢查Oracle監(jiān)聽服務(wù)和網(wǎng)絡(luò)連通性。筆者首先在服務(wù)器上tnsping實(shí)例名orcl，發(fā)現(xiàn)等了很久，返回操作超時(shí)錯(cuò)誤。信息如下：

-bash-3.2$ tnsping orcl

TNS Ping Utility for Solaris: Version 10.2.0.1.0 - Production on 18-JAN-2019 19:58:22

Copyright (c) 1997,2005, Oracle.All rights reserved.

Used parameter files:

/u01/app/oracle/product/10.2.0/db_1/network/admin/sqlnet.ora

Used TNSNAMES adapter to resolve the alias

Attempting to contact(DESCRIPTION = (ADDRESS= (PROTOCOL = TCP)(HOST= SUN)(PORT = 1521))(CONNECT_DATA = (SERVER =DEDICATED) (SERVICE_NAME= orcl)))

TNS-12535: TNS:operation timed out

接下來(lái)，筆者tnsping本機(jī)IP，返回結(jié)果正常。如下：

-bash-3.2$ tnsping 172.28.28.36

TNS Ping Utility for Solaris: Version 10.2.0.1.0 - Production on 18-JAN-2019 20:08:50

Copyright (c) 1997,2005, Oracle.All rights reserved.

Used parameter files:

/u01/app/oracle/product/10.2.0/db_1/network/admin/sqlnet.ora

Used EZCONNECT adapter to resolve the alias

Attempting to contact

(DESCRIPTION=(CONNECT_DATA=(SERVICE_NAME=172.28.28.36))(ADDRESS=(PROTOCOL=TCP)(HOST=172.28.28.36)(PORT=1521)))

OK (0 msec)

筆者懷疑監(jiān)聽服務(wù)存在問題，執(zhí)行“l(fā)snrctl stop” 和“l(fā)snrctl start”命令來(lái)重啟監(jiān)聽服務(wù)，發(fā)現(xiàn)故障提示依舊。接著執(zhí)行“l(fā)snrctl status”查看監(jiān)聽服務(wù)狀態(tài)。返回結(jié)果如圖1所示。

通過(guò)最后兩行，我們可以看出實(shí)例orcl監(jiān)聽處于未知狀態(tài)。orcl實(shí)例沒有注冊(cè)到監(jiān)聽服務(wù)中。于是，通過(guò)SQLPlus工具登錄數(shù)據(jù)庫(kù)進(jìn)行實(shí)例注冊(cè)。具體方法如下：

-bash-3.2$ sqlplus /nolog

SQL*Plus: Release 10.2.0.1.0 - Production on Fri Jan 18 20:10:51 2019

Copyright (c) 1982,2005, Oracle.All rights reserved.

SQL> conn system/rs_789 as sysdba;

Connected.

SQL> alter system register;

System altered.

圖1 執(zhí)行l(wèi)snrctl status查看監(jiān)聽服務(wù)狀態(tài)

圖2 查看Oracle監(jiān)聽服務(wù)相關(guān)日志

再次使用“l(fā)snrctl status”命令查看監(jiān)聽服務(wù)狀態(tài)，發(fā)現(xiàn)故障提示依舊。那看看配置文件是不是有問題呢？查看tnsnames.ora文件。配置如下：

ORCL =

(DESCRIPTION =

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

(CONNECT_DATA =

(SERVER = DEDICATED)

(SERVICE_NAME =orcl)

)

)

EXTPROC_CONNECTION_DATA =

(DESCRIPTION=

(ADDRESS_LIST =

(ADDRESS =(PROTOCOL = IPC)(KEY = EXTPROC1))

)

(CONNECT_DATA =

(SID =PLSExtProc)(PRESENTATION =RO)

)

該配置文件并未發(fā)現(xiàn)什么異常。接下來(lái)，筆者又查看了Oracle監(jiān)聽服務(wù)相關(guān)日志。最后幾行日志如圖2所示。

上面一直有警告提示，“Subscription for node down event still pending”。

故障解決

經(jīng)上網(wǎng)查詢相關(guān)資料，此錯(cuò)誤引起的原因可能由于監(jiān)聽無(wú)法在指定端口啟動(dòng)，前一次監(jiān)聽服務(wù)未正常退出或有其他程序占用端口。提示查看/etc/hosts相關(guān)配置。于是，筆者打開/etc/hosts文件，配置如下：

-bash-3.2$ cat /etc/hosts

#

# Internet host table

#

::1 localhost

127.0.0.1 localhost

222.*.*.* SUN loghost

172.28.28.36 WWW

果然發(fā)現(xiàn)一些問題，由于當(dāng)時(shí)服務(wù)器要對(duì)外網(wǎng)開放使用，服務(wù)器同時(shí)接入內(nèi)網(wǎng)和外網(wǎng)。但后來(lái)處于網(wǎng)絡(luò)安全考慮，所有服務(wù)器的外網(wǎng)都統(tǒng)一轉(zhuǎn)移到上層硬件防火墻進(jìn)行訪問控制。服務(wù)器只接入內(nèi)網(wǎng)。但/etc/hosts的配置信息并沒有做相應(yīng)修改。既然問題已找到，于是修改/etc/hosts文件，注意要先切換到root用戶，配置完成后要使用“wq!”，強(qiáng)制保存退出。更改后配置如下：

-bash-3.2# cat /etc/hosts

#

# Internet host table

#

::1 localhost

127.0.0.1 localhost

172.28.28.36 SU

最后再切換到Oracle用戶下，執(zhí)行l(wèi)snrctl stop命令和lsnrctl start命令重啟監(jiān)聽服務(wù)。剛開始監(jiān)聽服務(wù)還處于未知狀態(tài)，稍等約1分鐘，再次執(zhí)行l(wèi)snrctl status命令，可以看到實(shí)例監(jiān)聽處于Ready狀態(tài)。返回如下信息：

-bash-3.2$ lsnrctl status

LSNRCTL for Solaris:Version 10.2.0.1.0 -Production on 18-JAN-2019 20:11:35

Copyright (c) 1991,2005, Oracle.All rights reserved.

Connecting to (DESCRI PTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1)))

STATUS of the LISTENER

……

(DESCRIPTION=(AD DRESS=(PROTOCOL=tcp)(HOST=172.28.28.36)(PORT=1521)))

Services Summary...

Service "PLSExtProc"has 1 instance(s).

Instance"PLSExtProc", status UNKNOWN, has 1 handler(s)for this service...

Service "orcl" has 2 instance(s).

Instance "orcl",status UNKNOWN, has 1 handler(s) for this service...

Instance "orcl",status READY, has 1 handler(s) for this service...

Service "orclXDB" has 1 instance(s).

Instance "orcl",status READY, has 1 handler(s) for this service...

Service "orcl_XPT"has 1 instance(s).

Instance "orcl",status READY, has 1 handler(s) for this service...

The command completed successfully

通過(guò)本次故障可以發(fā)現(xiàn)，一個(gè)看似疑難的故障問題往往是由一個(gè)簡(jiǎn)單的配置文件錯(cuò)誤導(dǎo)致。所以，在我們今后的工作中，一定要扎扎實(shí)實(shí)學(xué)好理論基礎(chǔ)，面對(duì)故障問題才能迎刃而解。