Chapter 19. Tuning and Performance Analysis

The HP e3000 has a long-standing, well-deserved reputation for stellar performance in On-Line Transaction Processing (OLTP) applications. So much so, in fact, that often the best advice on MPE performance tuning is “Don't touch it!” I've heard more than one performance specialist lament that they can frequently solve clients' performance problems simply by un- doing the “adjustments” that the clients have tried to do for themselves. This chapter won't provide you with any magic spells that instantly double your system's processing power. Moreover, you should approach this material very deliberately, so that if you do stumble on something that looks a bit magical, you can avoid the fate of Mickey Mouse in Fantasia.

Performance analysis usually implies that there is a performance problem—or at least a perceived problem – that you want to solve. Understanding the source of the problem comes down to identifying a bottleneck—some scarce resource that is causing processes to wait, leaving other resources untapped. Once you have found the bottleneck, you can either find a way to put less demand on the scarce resource, or you can buy more of that resource. If the bottleneck is caused by a poorly written application program, perhaps it can be re-engineered to be more efficient. Or maybe your bottleneck is actually the result of a human factor. For instance, you may find out that the reason everything grinds to a halt at 4:30 PM every day is that there are 25 people in marketing who all wait until the end of the day to update their records. If they can agree to spread their activity throughout the day, they may have a less noticeable impact on the rest of your users.

Some bottlenecks are less obvious, though, and diagnosing them requires a deeper understanding of how MPE/iX works. In some cases, you may discover that your system has enough power to handle the load, but it needs to be told more specifically how to allocate resources to the different types of processes you are running. This is where tuning comes into play. Still not magic, but there are some commands and techniques that can improve overall performance when used correctly.