Mutexes And Changes in Library Cache - HrOUG
Mutexes And Changes in Library Cache - HrOUG
Mutexes And Changes in Library Cache - HrOUG
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DbProf.<br />
com<br />
“Cursor: p<strong>in</strong> S wait on X” waits<br />
• MOS ID 786507.1<br />
• A session waits on this event when request<strong>in</strong>g a mutex for shareable<br />
operations related to p<strong>in</strong>s (such as execut<strong>in</strong>g a cursor), but the mutex<br />
cannot be granted because it is be<strong>in</strong>g held exclusively by another session<br />
(which is most likely pars<strong>in</strong>g the cursor).<br />
• Causes:<br />
– Frequent Hard Parses<br />
• If the frequency of Hard Pars<strong>in</strong>g is extremely high, then contention can occur on this<br />
p<strong>in</strong>.<br />
– High Version Counts<br />
• When Version counts become excessive, a long cha<strong>in</strong> of versions needs to be<br />
exam<strong>in</strong>ed and this can lead to contention on this event<br />
• One of the most likely causes of cursor: p<strong>in</strong> S wait on X is high<br />
pars<strong>in</strong>g time.<br />
www.dbprof.com - © 2012 Jože Senegačnik<br />
Oracle ACE Director<br />
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