How to Identify Which Latch is Associated with a "latch free" wait

(Doc ID 413942.1)

Last updated on JULY 13, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 8.1.7.4 and later
Oracle Database - Personal Edition - Version 8.1.7.4 and later
Oracle Database - Standard Edition - Version 8.1.7.4 and later
Information in this document applies to any platform.

Goal

It is important to identify which latch is associated with latch free waits when tuning a database for latch waits. 

For versions prior to 10g, there is an umbrella wait event called latch free that covers all latch waits.  The specific latch or latches involved must be determined from either a 10046 trace (and TKProf) or from a statspack report.  This note will show you how to determine which latch or latches are associated with the latch free event.

Note: In Oracle 10g or later, finding which latches are causing waits is easy because most wait events have been introduced for specific latch waits (e.g., latch: shared pool).  However, some latch waits are still rolled up in the old latch free wait event and you will need to follow the procedure here to obtain more information. So this note can be used for later versions as well.

 

Solution

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