Craig Shallahamer's Blog
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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.
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©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>While not shown in Figure 3-13, more recent Oracle releases and Statspack reports will show the Time Waited column. The time waited value should be very close to the wait time reported by Oracle's wait interface. If so, then use this number to determine the latch that needs attention. If the Time Waited column is not provided, you'll need to manually calculate the Impact column, as discussed earlier. Just copy and paste the Statspack values into a spreadsheet and create an Impact column. The top latch should clearly rise above the rest.
p><p>Figure 3-13. A partial Statspack report based on Oracle9i Release 2. Only the Top 5 Timed Events section and the most active latches in the Latch Sleep Breakdown section are shown.
p><p>Table 3-2 is based on the Latch Sleep Breakdown section in Figure 3-13. The Impact column and the impact percentage were calculated, and the rows were sorted by the impact in descending order. Clearly, the library cache is the top latch and should be given priority. But in this case, the shared pool latch should also be addressed. So, the first priority is the library cache latch, followed by the shared pool latch. As you'll learn in Chapter 7, the library cache and shared pool latches are closely associated with cursor execution, so a change focused on one can affect the other.
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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