2026-03-12 20:23:15

vdh/latches.sql

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+/**********************************************************************
+ * File:	latches.sql
+ * Type:	SQL*Plus script
+ * Author:	Tim Gorman (Evergreen Database Technologies, Inc.)
+ * Date:	20-Sep-99
+ *
+ * Description:
+ *	Query to find the latches which are being waited on the longest.
+ *	GETS is the total number of times the latch is acquired.
+ *	IMMEDIATE_GETS is the number of times the latch was acquired
+ *	without waiting at all.  SPIN_GETS is the number of times that
+ *	the latch was not acquired immediately, but was acquired after
+ *	1-6 "spins" or "non-pre-emptive waits".  SLEEPS is the number
+ *	of times the latch was neither acquired immediately nor acquired
+ *	by non-pre-emptive waits, but instead required one or more
+ *	"pre-emptive waits" (i.e. the process went to "sleep",
+ *	relinquishing the CPU).  The latches with the most SLEEPS are
+ *	the site of the most contention...
+ *
+ *	Mind you, none of this is a problem unless the wait-event
+ *	"latch free" is one of the top five or ten problems in the
+ *	V$SYSTEM_EVENT view, when queried and sorted according to
+ *	the column TIME_WAITED.  If "latch free" is not a problem
+ *	overall, then it makes little sense to worry about the results
+ *	of this report...
+ *
+ * Modifications:
+ **********************************************************************/
+set echo off feedback off timing off trimspool on pages 1000 lines 500
+
+col name format a25 heading "Latch Name" truncate
+col gets format 9,999,999,990 heading "Total Gets"
+col immediate_gets format 9,999,999,990 heading "Immediate|Gets"
+col spin_gets format 999,990 heading "Spin Gets"
+col sleeps format 9,999,990 heading "Sleeps"
+col instance new_value V_INSTANCE noprint
+
+select  lower(replace(t.instance,chr(0),'')) instance
+from    v$thread        t,
+        v$parameter     p
+where   p.name = 'thread'
+and     t.thread# = to_number(decode(p.value,'0','1',p.value));
+
+select	name,
+	gets,
+	immediate_gets,
+	spin_gets,
+	sleeps
+from	v$latch
+where	gets > 0
+order by sleeps desc
+
+spool latches_&&V_INSTANCE
+/
+spool off