打补丁，尤其是升级TL，是有风险的。因此我们建议在生产系统中升级TL和打补丁时需要作好风险评估，保证升级后出现问题能够回退的原状态。
AIX OS能很好实现这点。
升级TL
1.到IBM fix central（http://www-933.ibm.com/support/fixcentral/）下载相应的TL补丁包
2.FTP至AIX服务器
3.运行升级命令smitty update_all,选择相应的目录
注意:
COMMIT software updates处选择NO，而SAVE replaced files?选择YES，否则无法回退。
我们按F1查看SAVE replaced files的帮助说明：
Indicates whether you want to save software files that are being replaced during installation。
YES instructs the system to save previous versions of software that is being replaced. In case of a failed installation, choosing YES allows the cleanup procedure to restore the previous version of the software. If you chose NO for "COMMIT software?", then you must choose YES to "SAVE replaced files?". Choosing YES will require some additional space to save replaced files. Choosing YES also requires more installation time because of the extra processing for saving files.
NO instructs the system NOT to save previous versions of software while it is being replaced. In case of a failed installation, the previous version of the software CANNOT be restored and is marked BROKEN. You must reinstall the software update if this occurs.
回退TL
1.smitty reject，在SOFTWARE name处选择需要回退的软件
2.屏幕返回OK即表示回退完成
Oslevel -r检查TL是否回退成功