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A Collective Effort

With Collection Services, you'll have performance data at your fingertips. If you do an Internet search on "collection services," you'll see mainly debt-collection services and waste-collection services. Fortunately, this article deals with neither. The real Collection Services, at least for the purposes of this article, is a function of i5/OS* that collects performance data at user-selected time intervals (between 15 seconds and one hour) from IBM* System i* hardware and software. The data collected is used by many system tools. I'll explain how Collection Services works and the philosophy behind its design.

Collection Services stores the raw data into a special system object called a Management Collection Object. It's interval-based (data collection happens at repeated time intervals), not trace-based (data collection happens whenever a specific event occurs). You can think of it as a snapshot of activity that's taken place up to the time that each interval data collection has taken place.

Design Philosophy

Collection Services was designed with the following objectives:

Always on. The function of performance collection should be thought of as an integral, essential part of the system. Users shouldn't have to think about it. Even though it can be started and stopped, it's best considered as something that's always running. If a user encounters a performance problem, it's not necessary to start collecting data to analyze the situation - the data is already there.

Efficient data collection. Collecting and storing the data should be quick and painless.

Release independent data. You shuld be able to collect the data on one machine, move it to another machine and process it on the second machine regardless of the i5/OS release of either one.

Regular, repeatable time intervals. Time intervals used for data collection should be multiples of each other and should occur on regular boundaries. For example, a 15-minute interval collection should always occur at 0, 15, 30 and 45 minutes past every hour. A 30-minute interval collection should always occur at 0 and 30 minutes past the hour.

Dave Legler is a staff software engineer with IBM. Dave can be reached at



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