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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Mutex Usage – “Cursor P<strong>in</strong>”<br />
• ‘library cache p<strong>in</strong>’ is replaced by a mutex and a ref count.<br />
Used for p<strong>in</strong>n<strong>in</strong>g (e.g. for execution), or compil<strong>in</strong>g a child<br />
cursor.<br />
• Used <strong>in</strong> 10.2.0.2+ and library cache p<strong>in</strong>s are not used any<br />
more (no ‘library cache p<strong>in</strong>’ wait events)<br />
• Used for:<br />
– P<strong>in</strong>n<strong>in</strong>g a cursor for execute<br />
• wait event: ‘cursor: p<strong>in</strong> S wait on X’<br />
– When p<strong>in</strong>n<strong>in</strong>g a cursor for execute, and the cursor is currently<br />
be<strong>in</strong>g exam<strong>in</strong>ed by another S<br />
• wait event ‘cursor: p<strong>in</strong> S’<br />
– Cursor rebuild<br />
• wait event (‘cursor: p<strong>in</strong> X‘).<br />
• This event should not be seen typically, because if a cursor is currently<br />
be<strong>in</strong>g used, and it needs to be rebuilt, another cursor will be created<br />
www.dbprof.com - © 2012 Jože Senegačnik<br />
Oracle ACE Director<br />
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