使用mksysb命令可以把系统备份到磁带上，精确的说法是mksysb主要用于创建rootvg上已挂接文件系统(mounted file systems)的可引导映像(bootable image)，并可用于系统崩溃时的状态恢复。需要注意的是，这里的可引导映像不包含以下类别：
1、用户定义的页面空间(User-defined paging spaces)
2、未挂接的文件系统(unmounted file systems)
3、裸设备(raw devices)
当使用mksysb时，有时需要把一些数据文件系统排除在映像之外,可通过编辑
/etc/exclude.rootvg文件来实现，比如我要排除/tmp：
# cat /etc/exclude.rootvg
^./tmp/
然后使用-e标志来执行mksysb
# mksysb -e /dev/rmt0
Creating information file (/image.data) for rootvg.
Creating tape boot image..............
bosboot: Boot image is 29316 512 byte blocks.
Creating list of files to back up.
Backing up 2679 files.....
2679 of 2679 files (100%)
0512-038 mksysb: Backup Completed Successfully.
bosboot: Boot image is 29316 512 byte blocks.
我这里排除的文件系统如下：
ERPDB1@/home/oracle>cat /etc/exclude.rootvg
^./backup_softs/
^./orasofts_bak/
^./orabak/
^./ora_arch/
备份方法：可通过smitty窗口或直接用命令行：
1，aix下可通过smitty mksysb -> Backup Device or File 选项设置备份目标地址（可选择磁带设备或文件系统），这里也可设置其他参数：
ERPDB1@/home/oracle>smitty mksysb
Back Up the System
Type or select values in entry fields.
Press Enter AFTER making all desired changes.
[Entry Fields]
WARNING: Execution of the mksysb command will
result in the loss of all material
previously stored on the selected
output medium. This command backs
up only rootvg volume group.
* Backup DEVICE or FILE [/dev/rmt0]
Create MAP files? no
EXCLUDE files? no
List files as they are backed up? no
Verify readability if tape device? no
Generate new /image.data file? yes
EXPAND /tmp if needed? no
Disable software packing of backup? no
Backup extended attributes? yes
Number of BLOCKS to write in a single output []
(Leave blank to use a system default)
注意这里的EXCLUDE files?要设置为yes才能使上面的/etc/exclude.rootvg文件指定的排除文件生效。
第二种方式就是直接用命令行了，效果一样：
/usr/bin/mksysb -i -e /dev/rmt0
要注意的是要选择好备份的时间，因为在备份过程中，应用程序可能会增删一些文件导致备份无法完全成功，这里记录一下碰到过的错误：
Creating information file (/image.data) for rootvg.
Creating tape boot image.......
bosboot: Boot image is 36911 512 byte blocks.
Creating list of files to back up..
Backing up 148474 files..............................
4301 of 148474 files (2%)..............................
23191 of 148474 files (15%)..............................
30763 of 148474 files (20%)..............................
34831 of 148474 files (23%)..............................
68121 of 148474 files (45%)..............................
68402 of 148474 files (46%)..............................
71022 of 148474 files (47%)..............................
81052 of 148474 files (54%)..............................
94251 of 148474 files (63%)..............................
100426 of 148474 files (67%)..............................
117739 of 148474 files (79%)..............................
131841 of 148474 files (88%)..............cannot access ./etc/perf/daily/xmwlm.090114: A file or directory in the path name does not
exist.
.....
0512-003 mksysb may not have been able to archive some files.
The messages displayed on the Standard Error contained additional
information.
这是因为/etc/perf/daily/ 下的文件只保留7天，可能备到那个文件的时候正好被删除了，所以提示找不到。还碰到过这样的提示：
78871 of 144459 files (54%).........cannot access ./u01/agent10g/sysman/emd/upload/rawdata.dat: A file or directory in the path name
does not exist.
cannot access ./u01/agent10g/sysman/emd/upload/mgmt_ha_mttr.dat: A file or directory in the path name does not exist.
后来查看：
p5b1@/#ls -l /u01/agent10g/sysman/emd/upload/rawdata.dat
-rw-r----- 1 oracle oinstall 29912 Jan 22 08:35 /u01/agent10g/sysman/emd/upload/rawdata.dat
p5b1@/#ls -l /u01/agent10g/sysman/emd/upload/mgmt_ha_mttr.dat
ls: 0653-341 The file /u01/agent10g/sysman/emd/upload/mgmt_ha_mttr.dat does not exist.
看来有一个文件是存在的，估计是备份的时间之后才生成的。这是oracle的oem相关的动态文件，应该不影响恢复。