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Category :
Database
Resources -> Database Administration
DB Version
:
Oracle 8i /
Oracle 9i
OS Details :
Sun Solaris9
Reference
: Oracle Metalink
Wait events occur in the
database when a session is waiting on a resource. The resource could
be data blocks or latches or enqueues. Oracle provided V$SESSION_WAIT
view is a good place to get information on waits experienced at the
individual session level. Statspack reports can also be run on the
database to get information on waits that occurred during a certain
interval. In this article we will look at some of the common wait
events that sessions experience in oracle. They include:
(1)
db file sequential read
(2)
db file scattered read
(3)
Buffer busy waits
(4)
Enqueue
(5) latch free
(6) direct path read
(7) direct path write
(8) Library cache pin
(9) SQL*NET message from dblink
(10) SQL*NET message from client
(11) Log File Sync
(12) Log File Parallel Write
V$SESSION_WAIT view provides
valuable information on the session waits. We can get information on
what P1, P2 and P3 columns mean within the V$SESSION_WAIT view by
querying the V$EVENT_NAME view. Click on each of the events listed
above to get detailed information on what those events mean, diagnosis
tips and possible ways of reducing those wait events.
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