一、基础知识

大家对RMAN我想都有不少的了解，此处只想对增量备份进行一下学习与实践，也是因为工作中确实有这样的需求存在。增量备份分为两种：Differential 差异，Cumulative 累积。如果不指明增量备份参数，默认的增量备份为Differential差异。常规备份方案：1周1次0级备份，其余为差异增量1级备份。或者1周1次0级备份，后两天为差异1级备份，第三天累积1级备份，后面0级备份前再次差异1级备份。总而言知，你了解了备份原理，后面策略就你自己定了。I believe you that you can choose correct policy.
（1）Differential Incremental Backups
差异增量备份，就是备份最近1次增量备份（差异或者累积）或者0级全备份后的所有变化的数据块。

（2）Cumulative Incremental Backups
累积增量备份，就是备份最近0级备份后的所有变化的数据块，所以占用空间是比较多些。

二、实验备份

（1）0级备份scripts：

#!/bin/bash

source /home/Oracle/.bash_profile

# Local variable
day=`date +%Y%m%d`
bk_dir=/rmanbackup/rman/TEST${day}

# Create backup directory
mkdir -p $bk_dir

# Incremental level 0 backup
rman target / log=$bk_dir/${day}.log <<EOF
RUN {
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '$bk_dir/%F';
ALLOCATE CHANNEL ch01 TYPE DISK MAXPIECESIZE=10G;
ALLOCATE CHANNEL ch02 TYPE DISK MAXPIECESIZE=10G;
BACKUP AS COMPRESSED BACKUPSET INCREMENTAL LEVEL 0 DATABASE SKIP INACCESSIBLE FILESPERSET 10 FORMAT '$bk_dir/db_%T_%U.bak' PLUS ARCHIVELOG FILESPERSET 20 DELETE ALL INPUT FORMAT '$bk_dir/arch_%T_%U.bak';
RELEASE CHANNEL ch01;
RELEASE CHANNEL ch02;
}
ALLOCATE CHANNEL FOR MAINTENANCE DEVICE TYPE DISK;
CROSSCHECK BACKUPSET;
DELETE NOPROMPT OBSOLETE;
EOF

（2）1级差异增量备份scripst：

点击(此处)折叠或打开

source /home/oracle/.bash_profile

# Create backup directory
mkdir -p bk_dir

# Differential Incremental level 1 backup
rman target / log=$bk_dir/${day}.log <<EOF
RUN {
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '$bk_dir/%F';
ALLOCATE CHANNEL ch01 TYPE DISK MAXPIECESIZE=10G;
ALLOCATE CHANNEL ch02 TYPE DISK MAXPIECESIZE=10G;
BACKUP AS COMPRESSED BACKUPSET INCREMENTAL LEVEL 1 DATABASE SKIP INACCESSIBLE FILESPERSET 10 FORMAT '$bk_dir/db_%T_%U.bak' PLUS ARCHIVELOG FILESPERSET 20 FORMAT '$bk_dir/arch_%T_%U.bak' DELETE ALL INPUT;
RELEASE CHANNEL ch01;
RELEASE CHANNEL ch02;
}
ALLOCATE CHANNEL FOR MAINTENANCE DEVICE TYPE DISK;
CROSSCHECK BACKUPSET;
DELETE NOPROMPT OBSOLETE;
EOF

（3）1级累积增量备份scripst：

# Cumulative Incremental level 1 backup
rman target / log=$bk_dir/${day}.log <<EOF
RUN {
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '$bk_dir/%F';
ALLOCATE CHANNEL ch01 TYPE DISK MAXPIECESIZE=10G;
ALLOCATE CHANNEL ch02 TYPE DISK MAXPIECESIZE=10G;
BACKUP AS COMPRESSED BACKUPSET INCREMENTAL LEVEL 1 CUMULATIVE DATABASE SKIP INACCESSIBLE FILESPERSET 10 FORMAT '$bk_dir/db_%T_%U.bak' PLUS ARCHIVELOG FILESPERSET 20 FORMAT '$bk_dir/arch_%T_%U.bak' DELETE ALL INPUT;
RELEASE CHANNEL ch01;
RELEASE CHANNEL ch02;
}
ALLOCATE CHANNEL FOR MAINTENANCE DEVICE TYPE DISK;
CROSSCHECK BACKUPSET;
DELETE NOPROMPT OBSOLETE;
EOF

三、总结
此次对增量备份进行了学习与实践，在实验过程中发现Differential Incremental 与 Cumulative Incremental的备份信息在rman中用list显示时都是1，无法分别。DBA们的看家本领，有备无患，所以每位DBA的小伙伴要学习好备份与恢复。Where there’s a will,there’s a way. Fighting Sam.

更多Oracle相关信息见Oracle专题页面http://www.linuxidc.com/topicnews.aspx?tid=12