重慶分公司
重慶分公司
一、現(xiàn)狀記錄
[oracle@node1 ~]$ /sbin/ifconfig eth2 Link encap:Ethernet HWaddr 00:25:90:04:AB:6B inet addr:192.168.9.140 Bcast:192.168.15.255 Mask:255.255.248.0 inet6 addr: fe80::225:90ff:fe04:ab6b/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:23530402 errors:0 dropped:0 overruns:0 frame:0 TX packets:10959123 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:15308483748 (14.2 GiB) TX bytes:10087987532 (9.3 GiB) --IP地址為192.168.9.140 [oracle@node1 ~]$ more /etc/hosts # Do not remove the following line, or various programs # that require network functionality will fail. 127.0.0.1 ecp-db localhost.localdomain localhost 192.168.9.140 node1.srtcloud.com --域名node1.srtcloud.com對應ip192.168.9.140 [oracle@node1 ~]$ lsnrctl status Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=node1.srtcloud.com)(PORT=1521))) STATUS of the LISTENER ------------------------ Alias LISTENER Version TNSLSNR for Linux: Version 10.2.0.5.0 - Production Start Date 04-NOV-2011 09:08:51 Uptime 21 days 4 hr. 58 min. 45 sec Trace Level off Security ON: Local OS Authentication SNMP OFF Listener Parameter File /opt/oracle/product/10.2.0/db_1/network/admin/listener.ora Listener Log File /opt/oracle/product/10.2.0/db_1/network/log/listener.log Listening Endpoints Summary... (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=node1.srtcloud.com)(PORT=1521))) Services Summary... Service "ecp" has 2 instance(s). Instance "ecp", status UNKNOWN, has 1 handler(s) for this service... Instance "ecp", status READY, has 1 handler(s) for this service... Service "ecpXDB" has 1 instance(s). Instance "ecp", status READY, has 1 handler(s) for this service... Service "ecp_XPT" has 1 instance(s). Instance "ecp", status READY, has 1 handler(s) for this service... Service "ora11g" has 2 instance(s). Instance "ora11g", status UNKNOWN, has 1 handler(s) for this service... Instance "ora11g", status READY, has 1 handler(s) for this service... Service "ora11gXDB" has 1 instance(s). Instance "ora11g", status READY, has 1 handler(s) for this service... The command completed successfully --說明:ora11g是oracle 11g，ecp是oracle 10g --當前使用域名node1.srtcloud.com監(jiān)聽 [oracle@node1 ~]$ more /opt/oracle/product/10.2.0/db_1/network/admin/tnsnames.ora # tnsnames.ora Network Configuration File: /opt/oracle/product/10.2.0/db_1/network/admin/tnsnames.ora # Generated by Oracle configuration tools. ECP = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = node1.srtcloud.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = ecp) ) ) ORA11G = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = node1.srtcloud.com)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = ora11g) ) ) --tns也通過域名訪問 [oracle@node1 ~]$ more /etc/resolv.conf nameserver 211.155.235.201 nameserver 211.155.235.188 --當前有效的DNS服務器 [oracle@node1 ~]$ more /etc/nsswitch.conf |grep hosts: hosts: files dns --域名解析順序 |
二、數(shù)據(jù)庫正常工作分析
1、tns工作：客戶端通過tns訪問數(shù)據(jù)庫，tns配置的是域名訪問，所以需要解析，因為此刻解析的順序是先利用/etc/hosts解析，所以讀取hosts文件，獲取到ip，然后訪問對應數(shù)據(jù)庫，和監(jiān)聽接觸。
2、監(jiān)聽工作：監(jiān)聽的是域名，其實也是通過hosts解析成ip的
3、這里能夠正常的工作，是因為hosts文件解析了域名
三、模擬數(shù)據(jù)庫訪問延遲
[oracle@node1 ~]$ more /etc/nsswitch.conf |grep hosts: hosts: dns files --先使用dns服務器解析，再使用hosts文件 [oracle@node1 ~]$ more /etc/resolv.conf nameserver 11.1.1.1 --無效的dns服務器 [oracle@node1 ~]$ sqlplus chf/xifenfei@ora11g SQL*Plus: Release 10.2.0.5.0 - Production on Fri Nov 25 14:44:55 2011 Copyright (c) 1982, 2010, Oracle. All Rights Reserved. --會在這里一個很長的時間等待 [oracle@node1 ~]$ lsnrctl status LSNRCTL for Linux: Version 10.2.0.5.0 - Production on 25-NOV-2011 14:48:26 Copyright (c) 1991, 2010, Oracle. All rights reserved. Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=node1.srtcloud.com)(PORT=1521))) --也會一個長時間的等待 --問題原因:就是因為解析域名的時候，先去訪問dns服務器，因為該ip非dns服務器ip，所以會一直等待該ip超時， --然后訪問hosts文件獲取ip地址（這個就是為什么我們登錄或者查看監(jiān)聽狀態(tài)的時候，會出現(xiàn)如此長的時間的等待） |
其實因為dns延遲的現(xiàn)象有很多種，我這里只是舉了一個最簡單，比較常見的例子，在處理因dns解析的監(jiān)聽延遲的問題上，可以參考下面幾點:
1、如果非特殊情況，盡可能使用ip地址在監(jiān)聽和tns中
2、如果是使用域名，請盡可能使用hosts解析，解析順序配置為files優(yōu)先（因為dns服務器有很多不確定，不可控因素）
3、如果一定要使用dns服務器解析，請把穩(wěn)定的dns服務器配置在第一項，盡可能避免出現(xiàn)dns服務器不可達或者不存在該域名的現(xiàn)象
