Database Availability
OK, your Web company just finished what they think is a great Web site, without asking much of you, which at this point is a good thing. You have lots going on and really don’t want to deal with that right now. Into the marking management meeting you go, and, what's this? You now need to provide access to your live data 24 hours a day! Did you miss a meeting sometime back?
No, you are told, the Web guys just built an Access DB to test with, now they just want to hook up the ODBC to your DB/2 system. "What's the problem?" they ask. "A simple PC can do this, why not that big antiquated host system?" Everything they read says the AS/400 will talk to the PC with no problem, "What's the big deal?"
Of course, you do your best not to throw your new laptop at the guy, and you look pleadingly at your boss who offers no solace at all. In fact she looks at you with a look of "Well, why isn't this done already?"
Slowly, you try to respond, knowing that you are in a no-win scenario, "It's a little more complicated than that." You pause, trying to gain control of what you know is a losing situation. "First off, we need time to back up the system. Second, I'm not sure I’m going to let you get in to the database directly. There are security issues, availability issues." You look around the room at the faces who stare blankly back at you.
You decide you need a new strategy. You tell them, "OK! We will be able to provide the availability, but the security is an issue and needs to be looked at." There really is not much they can say. Security is always a good out right now, but the availability issue, what the heck are you going to do with that?
The AS/400 and other host systems are built for availability. In the midrange market I don't think there is a system with a better reliability record. Especially with RAID and mirroring, even the disk problems have become less worrisome. But 24 hours is not exactly what you wanted to attempt. The backup, even with the high-speed tape takes a little over an hour. You don't have enough disk storage right now to backup to disk and then stream to tape.
Even with that, you would need some time to snapshot the disk. Save while active is an option, but you still need some time to check point the database. Journaling everything will work, but if you have to go through a recovery process for real, it will be really painful.
So now what? First, you think about the excuse they gave you for 24-hour availability. What if a customer wants to create an order or look at order status at 3:00 in the morning? The images in your head can't be pretty.
You’ve spent time in the past on disaster recovery and you’re pretty confident that you could get the organization back up and running within a day if something really nasty happened. But what these guys are asking for is not as easy as it sounds. It’s certainly not cheap, and every time you asked for more money for it, you got shot down. You were told, "We can afford a little down time if the recovery is that expensive." Of course they really didn’t think through the cost of the down time, but you weren't too concerned because the AS/400 just doesn’t go down other than disk failures, and you have that covered with RAID and mirroring. This new thing though: Yuck!
Actually, there are options for you. Some you can cram down the throat of the Web folks, which might feel good, but you know that for this to really work, it's your problem. The options you look at include, journaling, system mirroring, dual systems, database replication, and of course, you can always quit.
Assuming the last option is not high on your list, the others will all work, but each has plusses and minuses. Most of the minuses revolve around recovery complexity and budget. If you have the sophistication to handle a complicated recovery, then it will be cheaper, if not, you may be forced to spend the money to buy the capability to handle it for you.
What you find out after spending more time than you would like, is that there are more options than you have the time or patience to look at. Unfortunately, you have to look at them to come up with an answer that you are willing to live with. We have all read that the rules are changing, and that it will affect how we do things, what we are finding out now is they are affecting us in ways that we did not realize. But, not to worry, things are only changing at the speed of the Web... Oh, maybe that's not a good thing!
John Bussert is president of Swift Technologies (Marengo, Ill.), a firm specializing in AS/400 and Windows NT software. jbussert@stecnet.com