2026-03-12 20:23:15
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tpt/latchprof.sql
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tpt/latchprof.sql
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-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
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-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
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--------------------------------------------------------------------------------
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--
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-- File name: latchprof.sql ( Latch Holder Profiler )
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-- Purpose: Perform high-frequency sampling on V$LATCHHOLDER
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-- and present a profile of latches held by sessions
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--
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-- Author: Tanel Poder
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-- Copyright: (c) http://www.tanelpoder.com
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--
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-- Usage: @latchprof <what> <sid> <latch name> <#samples>
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-- @latchprof name 350 % 100000 - monitor all latches SID 350 is holding
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-- @latchprof sid,name % library 1000000 - monitor which SIDs hold latches with "library" in their name
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-- @latchprof sid,name,laddr % 40D993A0 100000 - monitor which SIDs hold child latch with address 0x40D993A0
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-- Other:
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-- The sampling relies on NESTED LOOP join method and having
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-- V$LATCHHOLDER as the inner (probed) table. Note that on 9i
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-- you may need to run this script as SYS as it looks like otherwise
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-- the global USE_NL hint is not propagated down to X$ base tables
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--
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-- The join in exec plan step 8 MUST be a NESTED LOOPS join, this is how
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-- the high speed sampling of changing dataset from V$LATCHHOLDER
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-- is done, otherwise you will not see correct results.
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--
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-- -----------------------------------------------------------------------------------------------
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-- | Id | Operation | Name | E-Rows | OMem | 1Mem | Used-Mem |
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-- -----------------------------------------------------------------------------------------------
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-- | 1 | MERGE JOIN CARTESIAN | | 1 | | | |
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-- | 2 | MERGE JOIN CARTESIAN | | 1 | | | |
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-- |* 3 | FIXED TABLE FULL | X$KSUTM | 1 | | | |
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-- | 4 | BUFFER SORT | | 1 | 9216 | 9216 | 8192 (0)|
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-- | 5 | VIEW | | 1 | | | |
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-- | 6 | SORT ORDER BY | | 1 | 2048 | 2048 | 2048 (0)|
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-- | 7 | SORT GROUP BY | | 1 | 9216 | 9216 | 8192 (0)|
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-- | 8 | NESTED LOOPS | | 1 | | | |
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-- | 9 | VIEW | | 1 | | | |
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-- | 10 | CONNECT BY WITHOUT FILTERING| | | | | |
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-- | 11 | FAST DUAL | | 1 | | | |
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-- |* 12 | FIXED TABLE FULL | X$KSUPRLAT | 1 | | | |
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-- | 13 | BUFFER SORT | | 1 | 9216 | 9216 | 8192 (0)|
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-- |* 14 | FIXED TABLE FULL | X$KSUTM | 1 | | | |
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-- -----------------------------------------------------------------------------------------------
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--
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-- If you want to drill down to latch child level, include "laddr" in first parameter
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-- to latchprof
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--
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-- Then you can use la.sql (V$LATCH_PARENT/V$LATCH_CHILDREN) to
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-- map the latch address back to latch child# if needed
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--
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--------------------------------------------------------------------------------
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-- what includes what columns to display & aggregate and also options like latch name filtering
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DEF _lhp_what="&1"
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DEF _lhp_sid="&2"
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DEF _lhp_name="&3"
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DEF _lhp_samples="&4"
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COL name FOR A40 WRAP
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COL latchprof_total_ms HEAD "Held ms" FOR 999999.999
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COL latchprof_pct_total_samples head "Held %" format 999.99
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COL latchprof_avg_ms HEAD "Avg hold ms" FOR 999.999
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COL dist_samples HEAD Gets
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COL total_samples HEAD Held
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BREAK ON lhp_name SKIP 1
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PROMPT
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PROMPT -- LatchProf 2.10 by Tanel Poder ( https://blog.tanelpoder.com )
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SET TERMOUT OFF
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SELECT DECODE(SUBSTR(BANNER, INSTR(BANNER, 'Release ')+8,1), 1, '', '--') latchprof_oraversion
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FROM v$version WHERE ROWNUM=1;
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SET TERMOUT ON
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WITH
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t1 AS (SELECT hsecs FROM v$timer),
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samples AS (
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SELECT /*+ ORDERED USE_NL(l) USE_NL(s) USE_NL(l.gv$latchholder.x$ksuprlat) NO_TRANSFORM_DISTINCT_AGG */
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&_lhp_what
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, COUNT(DISTINCT gets) dist_samples
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, COUNT(*) total_samples
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, COUNT(*) / &_lhp_samples total_samples_pct
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FROM
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(SELECT /*+ NO_MERGE */ 1 FROM DUAL CONNECT BY LEVEL <= &_lhp_samples) s,
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v$latchholder l,
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(SELECT
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sid indx
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, sql_hash_value sqlhash
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, sql_address sqladdr
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, sql_child_number sqlchild
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, sql_id sqlid
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FROM v$session) s
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WHERE
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l.sid LIKE '&_lhp_sid'
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AND (LOWER(l.name) LIKE LOWER('%&_lhp_name%') OR LOWER(RAWTOHEX(l.laddr)) LIKE LOWER('%&_lhp_name%'))
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AND l.sid = s.indx
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GROUP BY
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&_lhp_what
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ORDER BY
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total_samples DESC
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),
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t2 AS (SELECT hsecs FROM v$timer)
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SELECT /*+ ORDERED */
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&_lhp_what
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, s.total_samples
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, s.dist_samples
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-- , s.total_samples_pct
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, s.total_samples / &_lhp_samples * 100 latchprof_pct_total_samples
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, (t2.hsecs - t1.hsecs) * 10 * s.total_samples / &_lhp_samples latchprof_total_ms
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-- s.dist_events,
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, (t2.hsecs - t1.hsecs) * 10 * s.total_samples / dist_samples / &_lhp_samples latchprof_avg_ms
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FROM
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t1,
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samples s,
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t2
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WHERE ROWNUM <= 30
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/
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COL name CLEAR
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