数据库Oracle数据的异地的自动备份
数据库Oracle数据的异地的自动备份
正在看的ORACLE教程是:数据库Oracle数据的异地的自动备份。在大型商业应用中，数据的异地容灾备份十分重要，也必不可少。笔者根据自己的实践经验，设计了一套简洁地实现异地数据自动备份的方法，可供数据库管理人员参考。文中所有的程序都经过测试，运行良好。这里模拟的异地运行环境为一主一备两套Sun Solaris系统，所采用的备份方法为Oracle数据库提供的标准备份：export。相关命令
文中主要用到三个命令，这里先单独介绍一下:
export: 将数据库中数据备份成一个二进制系统文件，它有三种模式: 用户模式、表模式、整个数据库模式。还可分为三种备份类型：完全型、积累型、增量型。本文以整个数据库模式下的完全型为例说明。export使用格式为：
exp userid file
其中：userid的用法为username/userpassword，即Oracle中的用户名/口令。userid必须为exp的第一个参数，file指备份文件所放位置及名称。
ftp: 一般情况下可通过交互方式实现两台主机间的数据传输，即需要手工输入目标主机的IP地址、用户名、口令等。但是当用户使用ftp命令时，系统将会先在该用户的注册目录中寻找.netrc文件，并首先执行该文件。这样，我们可以通过编写一个.netrc的文件来达到自动备份的目的。要注意该文件必须命名为.netrc，且必须存放在启动ftp命令主机上的用户注册目录里。ftp常用选项：
-i：进行多文件传送时关闭交互提示；
-n：在连接之后不进行自动登录。
本文使用“-i”选项，以关闭交互提示。
crontab: cron是一个永久进程，它由/etc/rc.local启动执行。cron检查/var/spool/cron/crontabs/目录中的文件，找到所要执行的任务和执行任务的时间，并自动完成。该目录中文件由crontab命令建立。用户所建立的crontab文件存于/var/spool/cron/crontabs中，其文件名与用户名一致，本文使用crontab的用户为Oracle，所建立的文件名也为Oracle。
cron使用者的权限记载在下列两个文件中: /usr/var/adm/cron/cron.deny和/usr/var/adm/cron/cron.allow。前面的文件中所列的用户不允许使用crontab命令；后一文件中所列的用户允许使用crontab命令。crontab命令的常用格式为：
crontab -l：显示用户的crontab文件的内容；
crontab -r：从crontabs目录中删除用户的crontab文件；
crontab -e：编辑用户的crontab文件。
crontab文件每行中有6个字段，前5个为时间设定段，第6个为所要执行的命令。时间段分别为： minutes、hours、day of month、month、day of week，字段之间用空格或Tab分开。字段如果为“*”，表示该字段在所有可能的取值范围内取值; 如果一个字段是由连字符隔开的两个数字，表明命令可以在两个数字之间的范围内执行。
备份数据库
设定数据库的拥有者为Oracle，用户名为mistest，其口令为test，新建备份目录为/export/home/oracle/backup。建立一个命名为testbackup的备份文件，文件内容如下：
ORACLE-HOME=/export/home/oracle/815;export ORACLE-HOME
ORACLE-SID=ora815;export ORACLE-SID
rm /export/home/oracle/backup/*
rq=丶date +“%m%d”丶
/export/home/oracle/815/bin/exp mistest/test file=/export/home/oracle
/backup/exp$rq.dmp log=/exoport/home/oracle/backup/exp$rq.log
说明：前两句对Oracle数据库初始化，第3条语句清空备份目录，第4条语句建立一个取当前日期的变量，以便在最后一条语句的备份文件名里含有当前日期信息。
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异地传输
在备份主机里建立一个备份目录：/data/oradata/newbackup, 在本地主机Oracle用户的注册目录/export/home/oracle里建立一个.netrc文件。设定好备份主机的IP地址，备份主机上的用户为oraclebk, 口令为testbk2。.netrc文件内容为：
machine x.x.x..x
login oraclebk
password testbk2
macdef init
bin
lcd /export/home/oracle/backup
cd /data/oradata/backup
mput *
bye
说明: 前3条语句完成在备份主机上的登录，第４条语句定义一个名为init的宏，第５条语句表示以二进制传输，第６条语句表示进入本地工作目录，第７条语句表示进入备份主机目录，第８条语句完成将本地主机/export/home/oracle/backup目录下的所有文件传输至备份主机/data/oradata/backup目录下,最后一条语句退出ftp会话进程。
.netrc文件编写完成后，用命令“chmod 600
.netrc”使该文件只能被该用户所访问。
自动执行
我们以oracle用户登录本地主机，用“crontab －e”编写crontab文件用以启动自动备份进程。oracle文件内容如下：
10 23 * * * /export/home/oracle/testbackup
30 23 * * * ftp -i x.x.x.x
说明：第1条语句指定每天自动在23点10分执行对数据库的备份，第2条语句指定每天自动在23点半启动ftp,将备份文件传输到备份主机（备份主机为符合语句中指定IP地址的主机）。
Oracle文件只能在Oracle用户名下用“crontab －e”命令来编辑。编辑完成后，可以在用“crontab－l”命令来查看crontab文件内容，同时在/var/spool/cron/crontabs目录下查看是否增加了一个Oracle文件。
至此，本地主机可以每天定时备份数据库，并定时把备份数据传到备份主机。这样，较好地实现了Oracle数据异地自动备份，本地主机如果有什么故障，数据有了可靠备份，同时，在一定程度上也减轻了系统管理人员烦琐、重复的备份工作。
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