从Oracle 11gR2开始，引入SCAN(Single Client Access Name) IP的概念，相当于在客户端和数据库之间增加一层虚拟的网络服务层，即是SCAN IP和SCAP IP Listener。在客户端的tnsnames.ora配置文件中，只需要配置SCAN IP的配置信息即可，客户端通过SCAN IP、SCAN IP Listener来访问数据库。同之前各版本的RAC相比，使用SCAN IP的好处就是，当后台RAC数据库添加、删除节点时，客户端配置信息无需修改。可以通过配置DNS服务器或GNS来配置SCAN，我们这里以DNS为例来进行配置。
配置DNS服务器
这里，选择IP地址为172.16.0.176的服务器来配置DNS服务器。
①安装DNS软件包：
我们需要安装这三个rpm。
-rw-r–r– 1 root root 1015531 Apr 23 14:53 bind-9.3.6-4.P1.el5_4.2.x86_64.rpm
-rw-r–r– 1 root root 45360 Apr 23 14:53 bind-chroot-9.3.6-4.P1.el5_4.2.x86_64.rpm
-rw-r–r– 1 root root 62251 Apr 23 14:53 caching-nameserver-9.3.6-4.P1.el5_4.2.x86_64.rpm
大家有没有疑问这三个包，哪来的？身为菜鸟的我，就有这个疑问。
这三个包在linux的安装盘中有，我们通过挂载光盘可以找到。（具体操作百度，关键字mount）
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[root@rdd dns_rpm]# ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:0C:29:99:DA:22 inet addr:172.16.0.176 Bcast:172.16.15.255 Mask:255.255.240.0 inet6 addr: fe80::20c:29ff:fe99:da22/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:10237921 errors:0 dropped:0 overruns:0 frame:0 TX packets:1394986 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3375785216 (3.1 GiB) TX bytes:596171214 (568.5 MiB) [root@rdd dns_rpm]# pwd /root/dns_rpm [root@rdd dns_rpm]# ll total 1112 -rw-r–r– 1 root root 1015531 Apr 23 14:53 bind-9.3.6-4.P1.el5_4.2.x86_64.rpm -rw-r–r– 1 root root 45360 Apr 23 14:53 bind-chroot-9.3.6-4.P1.el5_4.2.x86_64.rpm -rw-r–r– 1 root root 62251 Apr 23 14:53 caching-nameserver-9.3.6-4.P1.el5_4.2.x86_64.rpm [root@rdd dns_rpm]# rpm -ivh bind-9.3.6-4.P1.el5_4.2.x86_64.rpm warning: bind-9.3.6-4.P1.el5_4.2.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 1e5e0159 Preparing… ########################################### [100%] 1:bind ########################################### [100%] [root@rdd dns_rpm]# rpm -ivh bind-chroot-9.3.6-4.P1.el5_4.2.x86_64.rpm warning: bind-chroot-9.3.6-4.P1.el5_4.2.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 1e5e0159 Preparing… ########################################### [100%] 1:bind-chroot ########################################### [100%] [root@rdd dns_rpm]# rpm -ivh caching-nameserver-9.3.6-4.P1.el5_4.2.x86_64.rpm warning: caching-nameserver-9.3.6-4.P1.el5_4.2.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 1e5e0159 Preparing… ########################################### [100%] 1:caching-nameserver ########################################### [100%] [root@rdd dns_rpm]# |
② 配置/var/named/chroot/etc/named.conf文件
先拷贝生成该文件：
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[root@rdd dns_rpm]# cd /var/named/chroot/etc/ [root@rdd etc]# ll total 16 -rw-r–r– 1 root root 405 Apr 18 07:50 localtime -rw-r—– 1 root named 1230 Jan 21 2010 named.caching-nameserver.conf -rw-r—– 1 root named 955 Jan 21 2010 named.rfc1912.zones -rw-r—– 1 root named 113 Apr 23 14:55 rndc.key [root@rdd etc]# cp -p named.caching-nameserver.conf named.conf [root@rdd etc]# |
修改后的该文件内容如下：
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[root@rdd etc]# pwd /var/named/chroot/etc [root@rdd etc]# cat named.conf // // named.caching-nameserver.conf // // Provided by Red Hat caching-nameserver package to configure the // ISC BIND named(8) DNS server as a caching only nameserver // (as a localhost DNS resolver only). // // See /usr/share/doc/bind*/sample/ for example named configuration files. // // DO NOT EDIT THIS FILE - use system-config-bind or an editor // to create named.conf - edits to this file will be lost on // caching-nameserver package upgrade. // options { listen-on port 53 { any; }; listen-on-v6 port 53 { ::1; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; memstatistics-file "/var/named/data/named_mem_stats.txt"; // Those options should be used carefully because they disable port // randomization // query-source port 53; // query-source-v6 port 53; allow-query { any; }; allow-query-cache { any; }; }; logging { channel default_debug { file "data/named.run"; severity dynamic; }; }; view localhost_resolver { match-clients { any; }; match-destinations { any; }; recursion yes; include "/etc/named.rfc1912.zones"; }; [root@rdd etc]# |
说明：为简单起见，将该文件中的127.0.0.1、localhost全部修改成any，且修改时，需要注意左右两边留空格。修改部分在上述配置文件中以红色加粗标示。
通过拷贝来生成/var/named/chroot/etc/named.conf文件时，注意加上-p选项，来保证文件的权限问题，否则会导致DNS服务启不来！
③ 配置Zone文件，修改/var/named/chroot/etc/named.rfc1912.zones文件
配置Zone的目的是为了解析SCAN IP，在该文件末尾添加以下反向Zone：什么是反向Zone，看到红色的部分了吗？我们配置的DNS IP是172.16.0.176，这回大家懂了吧！秒懂
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zone "0.16.172.in-addr.arpa." IN { type master; file "0.16.172.in-addr.arpa"; allow-update { none; }; }; |
配置反向Zone之后的该文件内容如下：
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[root@rdd etc]# pwd /var/named/chroot/etc [root@rdd etc]# ll total 20 -rw-r–r– 1 root root 405 Apr 18 07:50 localtime -rw-r—– 1 root named 1230 Jan 21 2010 named.caching-nameserver.conf -rw-r—– 1 root root 1200 Apr 23 15:03 named.conf -rw-r—– 1 root named 1085 Apr 23 15:19 named.rfc1912.zones -rw-r—– 1 root named 113 Apr 23 14:55 rndc.key [root@rdd etc]# cat named.rfc1912.zones // named.rfc1912.zones: // // Provided by Red Hat caching-nameserver package // // ISC BIND named zone configuration for zones recommended by // RFC 1912 section 4.1 : localhost TLDs and address zones // // See /usr/share/doc/bind*/sample/ for example named configuration files. // zone "." IN { type hint; file "named.ca"; }; zone "localdomain" IN { type master; file "localdomain.zone"; allow-update { none; }; }; zone "localhost" IN { type master; file "localhost.zone"; allow-update { none; }; }; zone "0.0.127.in-addr.arpa" IN { type master; file "named.local"; allow-update { none; }; }; zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa" IN { type master; file "named.ip6.local"; allow-update { none; }; }; zone "255.in-addr.arpa" IN { type master; file "named.broadcast"; allow-update { none; }; }; zone "0.in-addr.arpa" IN { type master; file "named.zero"; allow-update { none; }; }; zone "0.16.172.in-addr.arpa." IN { type master; file "0.16.172.in-addr.arpa"; allow-update { none; }; }; [root@rdd etc]# |
说明：正常情况下还应该配置正向Zone文件。这里，我们的RAC双节点node1、node2的域名domain都设置为localdomain，而默认情况下，该配置文件(/var/named/chroot/etc/named.rfc1912.zones)的第15行到第20行中已经自带下述正向Zone文件配置信息，所以无需再添加。
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zone "localdomain" IN { type master; file "localdomain.zone"; allow-update { none; }; }; |
④ 配置正、反向解析数据库文件。在/var/named/chroot/var/named路径下进行配置
首先，生成正、反向解析数据库文件。利用/var/named/chroot/var/named/localhost.zone复制生成正向解析的数据库文件，利用/var/named/chroot/var/named/named.local复制生成名为0.16.172.in-addr.arpa的反向解析的数据库文件。
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[root@rdd etc]# pwd /var/named/chroot/etc [root@rdd etc]# cd /var/named/chroot/var/named/ [root@rdd named]# ll total 36 drwxrwx— 2 named named 4096 Aug 26 2004 data -rw-r—– 1 root named 198 Jan 21 2010 localdomain.zone -rw-r—– 1 root named 195 Jan 21 2010 localhost.zone -rw-r—– 1 root named 427 Jan 21 2010 named.broadcast -rw-r—– 1 root named 1892 Jan 21 2010 named.ca -rw-r—– 1 root named 424 Jan 21 2010 named.ip6.local -rw-r—– 1 root named 426 Jan 21 2010 named.local -rw-r—– 1 root named 427 Jan 21 2010 named.zero drwxrwx— 2 named named 4096 Jul 27 2004 slaves [root@rdd named]# cp -p named.local 0.16.172.in-addr.arpa [root@rdd named]# ll total 40 -rw-r—– 1 root named 426 Apr 23 16:10 0.16.172.in-addr.arpa drwxrwx— 2 named named 4096 Aug 26 2004 data -rw-r—– 1 root named 198 Jan 21 2010 localdomain.zone -rw-r—– 1 root named 195 Jan 21 2010 localhost.zone -rw-r—– 1 root named 427 Jan 21 2010 named.broadcast -rw-r—– 1 root named 1892 Jan 21 2010 named.ca -rw-r—– 1 root named 424 Jan 21 2010 named.ip6.local -rw-r—– 1 root named 426 Jan 21 2010 named.local -rw-r—– 1 root named 427 Jan 21 2010 named.zero drwxrwx— 2 named named 4096 Jul 27 2004 slaves [root@rdd named]# |
说明：在上述步骤③中我们没有配置正向Zone文件，故只需生成反向解析数据库文件，正向解析数据库文件利用默认的localdomain.zone文件。
生成的正、反向解析数据库文件名一定要同上述步骤③中定义的正、反向Zone文件一致，否则DNS出错！
然后，定义正、反向解析数据库文件。
在正向解析数据库文件localdomain.zone末尾添加下述内容：
scan-cluster IN A 172.16.0.203
添加后内容如下：
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[root@rdd named]# pwd /var/named/chroot/var/named [root@rdd named]# cat localdomain.zone $TTL 86400 @ IN SOA localhost root ( 42 ; serial (d. adams) 3H ; refresh 15M ; retry 1W ; expiry 1D ) ; minimum IN NS localhost localhost IN A 127.0.0.1 scan-cluster IN A 172.16.0.203 [root@rdd named]# |
在反向解析数据库文件0.16.172.in-addr.arpa末尾添加下述内容：
203 IN PTR scan-cluster.localdomain.
添加后内容如下：
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[root@rdd named]# pwd /var/named/chroot/var/named [root@rdd named]# cat 0.16.172.in-addr.arpa $TTL 86400 @ IN SOA localhost. root.localhost. ( 1997022700 ; Serial 28800 ; Refresh 14400 ; Retry 3600000 ; Expire 86400 ) ; Minimum IN NS localhost. 1 IN PTR localhost. 203 IN PTR scan-cluster.localdomain. [root@rdd named]# |
测试DNS服务器解析SCAN IP正常
首先，在DNS服务器172.16.0.176上启动DNS服务：
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[root@rdd named]# /etc/init.d/named status rndc: connect failed: 127.0.0.1#953: connection refused named is stopped [root@rdd named]# /etc/init.d/named start Starting named: [ OK ] [root@rdd named]# /etc/init.d/named status number of zones: 7 debug level: 0 xfers running: 0 xfers deferred: 0 soa queries in progress: 0 query logging is OFF recursive clients: 0/1000 tcp clients: 0/100 server is up and running named (pid 23307) is running… [root@rdd named]# chkconfig named on [root@rdd named]# |
然后，分别在RAC节点node1、node2的/etc/resolv.conf配置文件中添加下述配置信息：
search localdomain
nameserver 172.16.0.176
添加之后：
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[root@node1 ~]# cat /etc/resolv.conf search localdomain nameserver 172.16.0.176 [root@node1 ~]# |
最后，测试SCAN IP解析是否成功？
node1测试：
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[root@node1 ~]# nslookup 172.16.0.203 Server: 172.16.0.176 Address: 172.16.0.176#53 203.0.16.172.in-addr.arpa name = scan-cluster.localdomain. [root@node1 ~]# nslookup scan-cluster.localdomain Server: 172.16.0.176 Address: 172.16.0.176#53 Name: scan-cluster.localdomain Address: 172.16.0.203 [root@node1 ~]# nslookup scan-cluster Server: 172.16.0.176 Address: 172.16.0.176#53 Name: scan-cluster.localdomain Address: 172.16.0.203 [root@node1 ~]# |
node2测试：
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[root@node2 ~]# nslookup 172.16.0.203 Server: 172.16.0.176 Address: 172.16.0.176#53 203.0.16.172.in-addr.arpa name = scan-cluster.localdomain. [root@node2 ~]# nslookup scan-cluster.localdomain Server: 172.16.0.176 Address: 172.16.0.176#53 Name: scan-cluster.localdomain Address: 172.16.0.203 [root@node2 ~]# nslookup scan-cluster Server: 172.16.0.176 Address: 172.16.0.176#53 Name: scan-cluster.localdomain Address: 172.16.0.203 [root@node2 ~]# |
至此，准备工作中的配置SCAN IP通过配置DNS服务器来解析已经成功！