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by Craig Shallahamer Get the book here |
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Craig Shallahamer's Blog
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. ------------------------------- Figure 3-10. The v$system_event based OSM swpctx.sql report. Clearly, latch contention is significant, and the latch to focus on is the CBC latch. Figure 3-11. The v$session_wait-based OSM swswp.sql report details sessions currently posting a wait event containing latch%free. We caught three sessions waiting for latch number 116, which the second v$latchname-based query shows as being the CBC latch. We know this is a pre-10g system because the latch name is not part of the wait event. If the Oracle release is earlier than Oracle Database 10g, the latch name is not part of the latch free wait event; therefore, additional actions must occur to determine the specific latch requiring our close attention. You have two basic options. One is to sample the system interactively based on the real-time wait event view, v$session_wait. The other option is to very carefully sample from the classic latch performance view, v$latch. 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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