在数据库mount或者open阶段，我们可以使用backup database备份整个数据库。
也可以使用configure exclude命令在配置中默认在全备时排除某个表空间不备份，也可以在backup时指定 noexclude不排除某个表空间。
备份数据的步骤：
1.使用RMAN连接目标库
2.确认数据库是mount或者open阶段
3.使用backup database命令备份数据库。在备份之前应该确认configuration中的默认值，然后根据实际情况添加参数，如果channel，format，plus archivelog等等。
默认值中备份了spfile和controlfile，示例分配两个channel备份全库
[oracle@lzl ~]$ vi /home/oracle/full_backup.sql
[oracle@lzl ~]$ cat /home/oracle/full_backup.sql
run{
allocate channel c1 type disk;
allocate channel c2 type disk;
backup database format '/home/oracle/rman_full_%T_%u';
release channel c1;
release channel c2;
}
 RMAN> @/home/oracle/full_backup.sql
RMAN> run{
2> allocate channel c1 type disk;
3> allocate channel c2 type disk;
4> backup database format '/home/oracle/rman_full_%T_%u';
5> release channel c1;
6> release channel c2;
7> }
released channel: ORA_DISK_1。   —release了默认值中的channel
allocated channel: c1
channel c1: SID=1 device type=DISK
allocated channel: c2
channel c2: SID=43 device type=DISK。 —每个channel拥有独立的sid
Starting backup at 2017-07-25 16:48:13
channel c1: starting full datafile backup set
channel c1: specifying datafile(s) in backup set
input datafile file number=00001 name=/u01/app/oracle/oradata/test/system01.dbf
input datafile file number=00004 name=/u01/app/oracle/oradata/test/users01.dbf
channel c1: starting piece 1 at 2017-07-25 16:48:13
channel c2: starting full datafile backup set
channel c2: specifying datafile(s) in backup set
input datafile file number=00002 name=/u01/app/oracle/oradata/test/sysaux01.dbf
input datafile file number=00003 name=/u01/app/oracle/oradata/test/undotbs01.dbf
channel c2: starting piece 1 at 2017-07-25 16:48:13。  —两个channel分别备份了两个数据文件。
channel c1: finished piece 1 at 2017-07-25 16:48:28
piece handle=/home/oracle/rman_full_20170725_0asa8fad tag=TAG20170725T164813 comment=NONE
channel c1: backup set complete, elapsed time: 00:00:15
channel c1: starting full datafile backup set
channel c1: specifying datafile(s) in backup set
channel c2: finished piece 1 at 2017-07-25 16:48:28
piece handle=/home/oracle/rman_full_20170725_0bsa8fad tag=TAG20170725T164813 comment=NONE
channel c2: backup set complete, elapsed time: 00:00:15
channel c2: starting full datafile backup set
channel c2: specifying datafile(s) in backup set
including current SPFILE in backup set。
channel c2: starting piece 1 at 2017-07-25 16:48:28
including current control file in backup set。
channel c1: starting piece 1 at 2017-07-25 16:48:29
channel c2: finished piece 1 at 2017-07-25 16:48:29
piece handle=/home/oracle/rman_full_20170725_0dsa8fas tag=TAG20170725T164813 comment=NONE
channel c2: backup set complete, elapsed time: 00:00:01
channel c1: finished piece 1 at 2017-07-25 16:48:30
piece handle=/home/oracle/rman_full_20170725_0csa8fas tag=TAG20170725T164813 comment=NONE
channel c1: backup set complete, elapsed time: 00:00:01
Finished backup at 2017-07-25 16:48:30。  —每个backup piece都是同一个tag
released channel: c1
released channel: c2。   —释放channel
RMAN> **end-of-file**
[oracle@lzl ~]$ ls -lrth rman_full_*
-rw-r----- 1 oracle oinstall 490M Jul 25 16:48 rman_full_20170725_0bsa8fad
-rw-r----- 1 oracle oinstall 998M Jul 25 16:48 rman_full_20170725_0asa8fad
-rw-r----- 1 oracle oinstall  96K Jul 25 16:48 rman_full_20170725_0dsa8fas
-rw-r----- 1 oracle oinstall 9.4M Jul 25 16:48 rman_full_20170725_0csa8fas
[oracle@lzl ~]$ strings rman_full_20170725_0dsa8fas |more
}|{z
TEST
TAG20170725T164813
TEST
test.__db_cache_size=729808896
test.__java_pool_size=4194304
…
strings的开头几行可以查看目标库和tag，如果是spfile还可以清楚的看到参数设置

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