Craig Shallahamer's Blog
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You were brought to this page based on an internet search
and as a free service to Oracle DBAs.
The text below is an except from the book,
Oracle Performance Firefighting, written by
Craig Shallahamer of
OraPub, Inc.
Figures and tables are not included on this page, only their reference.
To order the book in either print or PDF form, click
here.
©2009, 2010 by Craig Shallahamer. This is copyrighted material.
Please—Out of respect for those involved in the creation of the book and also for
their familes, we ask you to respect the copyright both in intent and deed. Thank you.
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<p>There can be a difference between the rate of transaction arrivals (or entry) and the rate of transaction exits. The actual transactions being processed is known as the workload. A system is deemed stable when, on average, the transaction entries equal the transaction exits. If this does not occur, eventually either so many transactions will build up on the system that it will physically shut down, or there will be so few transactions that no work will be performed. Because of this equality, for our work with Oracle systems, it is acceptable to refer to the arrival rate as the workload and vice versa. Use the term that makes your work easily understandable for your audience.
</p><p>The arrival rate symbol is universal in all publications and it is the Greek letter lambda. For the example of an arrival rate (the work performed over a period of time) of 9,000 transactions over a 30-minute period, using symbols and converting to seconds, the arrival rate calculation is as follows:
</p><p>Figure 9-1 is an actual Statspack report from an Oracle Database 10g Release 2 system that was experiencing severe cache buffer chain (CBC) latch contention. The Load Profile section appears near the top of both the Statspack and AWR reports. Over the Statspack reporting duration, on average, Oracle processed 0.22 transaction each second, 145,325 logical IOs per second, and 415 user calls per second. These reports have captured an initial value and ending value from a specific statistic, such as commits, database calls, or perhaps redo generated.
</p>
©2009, 2010 by Craig Shallahamer. This is copyrighted material.
Please—Out of respect for those involved in the creation of the book and also for
their familes, we ask you to respect the copyright both in intent and deed. Thank you.
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