Admin Alert: Meditations on Full System Backups
June 27, 2007 Joe Hertvik
Long-time i5/OS and OS/400 administrators may think they know everything about full system backups (FSBs). However, there are several considerations to think about before performing an FSB, and IBM has recently slipped additional capabilities into the FSB process that you may not know about. So let’s take five minutes and meditate over the whys, whens, and hows of FSBs and how you can improve the backup process in your shop.
Why We FSB
Full system backups are performed as insurance for emergency situations, such as a total system crash or a full system recovery to another machine in the event of a complete disaster (fire, flood, etc). FSBs take a complete snapshot of your machine (operating system, security, configurations, and data) that can be restored back to the machine or to another machine in a different location. When restoring from a FSB, the ideal situation is that the restored machine is an exact operational duplicate of the original box.
Because of the need to back up everything on your operating system, i5/OS requires that you put your iSeries or i5 box into restricted mode before performing an FSB, so that you can back up all system objects, including the operating system, that are locked during regular operations.
The mechanics of an FSB are simple and they are discussed in an earlier article I wrote called Dissecting an Option 21 Save. For an explanation of the ins and outs of putting your system i box into restricted mode, see Getting In and Out of iSeries Restricted State.
When We FSB
Since it can be a hassle taking down and backing up your entire system, you will want to be choosy about exactly when you should perform your FSB. If your shop IPLs its partitions every week, it’s easy to schedule an FSB because you have more opportunities for backing up the system. However, if your system i, i5, or iSeries box participates in real-time transactions in a 24x7x365 environment, scheduling an FSB can be more difficult. Therefore, it’s helpful to create some guidelines for what situations offer full system backup opportunities. I generally consider performing a full system backup when any of the following events occur.
The Alternative FSB
One of the problems with FSBs is that depending on how much data you have on your system, they can take several hours. Depending on how heavily used your system i, i5, or iSeries box is, a backup can put you in a severe time crunch, especially if you’re trying to perform two full system backups during an upgrade. An alternative to performing a time-consuming full system backup is to do the following:
By doing these steps, you save time in restricted mode by just backing up your core system objects that need the system down to be saved. And because you are taking regular backups of your data, you can easily perform a restore by using the two different tapes: the system backup (which doesn’t change as often) and the latest save-while-active backup that contains your rapidly changing data and configurations.
Changes to the FSB
In addition to all this, you may not realize that IBM has been adding new options to its full system backup strategy. In i5/OS V5R3, IBM made it possible to run batch jobs in the i5/OS controlling subsystem while the machine is in restricted mode. This means that you can set up a procedure to place your system i box into restricted mode, perform a batch system backup in the controlling subsystem, and then restart your system. I haven’t yet tested this technique but I will explore it in a future column. If you want read a little more about batch system saves before then, check out IBM’s Software Technical Document on Running a Full System Save or SAVSYS in Restricted State Batch.
The other significant FSB change occurred in i5/OS V5R4, when IBM introduced the Save System Information command (SAVSYSINF). SAVSYSINF allows you to save the cumulative changes that have occurred to your licensed internal code and QSYS library since the last Save System command (SAVSYS) was completed, and you don’t need to be in restricted mode to run SAVSYSINF. For restoration, you would need to apply two sets of backup media to restore the system to its last known operating system configuration: the media that contained your last system save and the media containing your SAVSYSINF info. For more information on using SAVSYSINF, see IBM’s entry on the subject in the i5/OS Information Center, Version 5, Release 4.
About Our Testing Environment
Most configurations described in this article were tested on an i5 550 box running i5/OS V5R3. Many of the commands may also be available in earlier versions of the operating system, except where a command is noted to have minimum operating system requirements. . . . However, if a command is present in earlier versions of the i5/OS or OS/400 operating systems, you may notice some variations in the pre-V5R3 copies of these commands. These differences may be due to command improvements that have occurred from release to release.