Craig Shallahamer's Blog
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You were brought to this page based on an internet search
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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>Figure 6-25. This sample v$session_wait-based OSM script swswp.sql displays the session numbers along with their wait event parameters for a given wait event. In this situation, we are looking for buffer busy waits parameter values and parameter value patterns.
p><p>Every Oracle block buffer is part of an Oracle segment. Every Oracle segment is a segment type, such as a data segment, index segment, undo segment, or temporary segment. The solution set is based, in part, on the segment type. Using the buffer busy wait event's p1 (file number) and p2 (block number) gathered in step 1, the segment type can be determined from a query based on dba_extents and dba_data_files, such as the one shown in Figure 6-26.
p><p>On a large Oracle system with hundreds of thousands of extents, querying dba_extents can take an unexpectedly long time. This is one reason why I force an additional step to run a query like the one in Figure 6-26. For performance reasons, some DBAs will periodically make a copy of the dba_extents view and run their report based on the copy. Unless a real-time copy of the extent situation is needed (which isn't the case in this example), dba_extents-based queries can run noticeably faster.
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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