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Home -> Community -> Mailing Lists -> Oracle-L -> Performance analysis (enqueue and buffer busy waits)
Hi list:
I've been analyzing an instance's performance for some time. I found a lot of enqueue and a lot of buffer busy waits.
Tracing the instance's sessions for some time I found that enqueue waits are mostly because of FK not being indexed. This of course generated shared locks (level 4) over child tables when a parent row was updated, deleted or inserted. I can solve this by creating the missing indexes.
In reference to the Buffer busy waits, mostly of these waits takes place over TABLES and p3=0 in all cases. I think that p3=0 indicates that a session wants a block that is being read from disk by another session. Keeping the object in memory will solve this problem, but unfortunately this is not an option as I'm working with Oracle 7.3.4. and the tables are big. I think that a lot of queries are using these TABLES.
The question is what can I do to solve this BBW?
And another curiosity question, can enqueue waits generate buffer busy waits ? (as a session is waiting for some buffer that another session is holding in an incompatible mode)
TIA
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