Performance tuning for IBM i: The basics and beyond

Disclaimer: The following information is based on over 20 years of experience with small AS/400's and over 30 years working with computers. The guidelines presented here that have served me well. Your mileage will vary depending upon factors such as hardware, software, users, time of day and possibly the phase of the moon.

The high performance of today's machines along with the improvements of the operating system in general and the Automatic Performance Tuner in particular have made most of these suggestions much less important than with earlier machines and operating system release levels.

Below are five questions that were posed by a Search400.com reader. I have provided very brief answers immediately following the questions. At the end of the questions I have provided some additional details about Question 2.

Additional details for Question 2:

Recommendations:

Below are two screen shots of the WRKSYSSTS screen that I will use when discussing the particular columns. The views of this screen shown were obtained by pressing the F21 key and selecting Advanced Assistance Level (shown first).

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Selecting Advance Assistance Level. Click on image for larger version.

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WRKSYSSTS screenshot 1. Click on image for larger version.

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WRKSYSSTS screenshot 2. Click on image for larger version.

Basic interactive tuning:
Before making any changes, I recommend taking a screen shot of the current configuration and setting the system value QPFRADJ = 0. On the WRKSYSSTS screen shots above I have labeled the columns A-G to clearly identify which column I am referring to.

The goals for good performance are:

The Columns "Pool Size" and "Max Active" are your adjusting knobs. Everything from here on is predicated on how much memory the system has. The fix for many performance issues is more memory. The following will help you make the best use of the memory you have for your particular environment.

Additional questions and answers regarding performance tuning were submitted following the publication of this tip. Ray has answered these questions specific to fault rates and pools in performance tuning on the AS/400 in a blog post.

ABOUT THE AUTHOR: Raymond G. Johnson is owner of and consulant at iSolutions Consulting Inc. in Eugene, Ore. He has over 30 years of experience with IBM hardware and software systems and provides technical support for i5, System i, iSeries and/or AS/400. If you have further performance tuning questions, Ray is available to answer them. Please submit your question to editor@search400.com.

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