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-- Copyright 2018 Tanel Poder. All rights reserved. More info at http://tanelpoder.com
-- Licensed under the Apache License, Version 2.0. See LICENSE.txt for terms & conditions.
--------------------------------------------------------------------------------
--
-- File name: latchprof.sql ( Latch Holder Profiler )
-- Purpose: Perform high-frequency sampling on V$LATCHHOLDER
-- and present a profile of latches held by sessions
--
-- Author: Tanel Poder
-- Copyright: (c) http://www.tanelpoder.com
--
-- Usage: @latchprof <what> <sid> <latch name> <#samples>
-- @latchprof name 350 % 100000 - monitor all latches SID 350 is holding
-- @latchprof sid,name % library 1000000 - monitor which SIDs hold latches with "library" in their name
-- @latchprof sid,name,laddr % 40D993A0 100000 - monitor which SIDs hold child latch with address 0x40D993A0
-- Other:
-- The sampling relies on NESTED LOOP join method and having
-- V$LATCHHOLDER as the inner (probed) table. Note that on 9i
-- you may need to run this script as SYS as it looks like otherwise
-- the global USE_NL hint is not propagated down to X$ base tables
--
-- The join in exec plan step 8 MUST be a NESTED LOOPS join, this is how
-- the high speed sampling of changing dataset from V$LATCHHOLDER
-- is done, otherwise you will not see correct results.
--
-- -----------------------------------------------------------------------------------------------
-- | Id | Operation | Name | E-Rows | OMem | 1Mem | Used-Mem |
-- -----------------------------------------------------------------------------------------------
-- | 1 | MERGE JOIN CARTESIAN | | 1 | | | |
-- | 2 | MERGE JOIN CARTESIAN | | 1 | | | |
-- |* 3 | FIXED TABLE FULL | X$KSUTM | 1 | | | |
-- | 4 | BUFFER SORT | | 1 | 9216 | 9216 | 8192 (0)|
-- | 5 | VIEW | | 1 | | | |
-- | 6 | SORT ORDER BY | | 1 | 2048 | 2048 | 2048 (0)|
-- | 7 | SORT GROUP BY | | 1 | 9216 | 9216 | 8192 (0)|
-- | 8 | NESTED LOOPS | | 1 | | | |
-- | 9 | VIEW | | 1 | | | |
-- | 10 | CONNECT BY WITHOUT FILTERING| | | | | |
-- | 11 | FAST DUAL | | 1 | | | |
-- |* 12 | FIXED TABLE FULL | X$KSUPRLAT | 1 | | | |
-- | 13 | BUFFER SORT | | 1 | 9216 | 9216 | 8192 (0)|
-- |* 14 | FIXED TABLE FULL | X$KSUTM | 1 | | | |
-- -----------------------------------------------------------------------------------------------
--
-- If you want to drill down to latch child level, include "laddr" in first parameter
-- to latchprof
--
-- Then you can use la.sql (V$LATCH_PARENT/V$LATCH_CHILDREN) to
-- map the latch address back to latch child# if needed
--
--------------------------------------------------------------------------------
-- what includes what columns to display & aggregate and also options like latch name filtering
DEF _lhp_what="&1"
DEF _lhp_sid="&2"
DEF _lhp_name="&3"
DEF _lhp_samples="&4"
COL name FOR A40 WRAP
COL latchprof_total_ms HEAD "Held ms" FOR 999999.999
COL latchprof_pct_total_samples head "Held %" format 999.99
COL latchprof_avg_ms HEAD "Avg hold ms" FOR 999.999
COL dist_samples HEAD Gets
COL total_samples HEAD Held
BREAK ON lhp_name SKIP 1
DEF _IF_ORA_10_OR_HIGHER="--"
PROMPT
PROMPT -- LatchProf 2.02 by Tanel Poder ( http://www.tanelpoder.com )
COL latchprof_oraversion NEW_VALUE _IF_ORA_10_OR_HIGHER
SET TERMOUT OFF
SELECT DECODE(SUBSTR(BANNER, INSTR(BANNER, 'Release ')+8,1), 1, '', '--') latchprof_oraversion
FROM v$version WHERE ROWNUM=1;
SET TERMOUT ON
WITH
t1 AS (SELECT hsecs FROM v$timer),
samples AS (
SELECT /*+ ORDERED USE_NL(l) USE_NL(s) USE_NL(l.gv$latchholder.x$ksuprlat) NO_TRANSFORM_DISTINCT_AGG */
&_lhp_what
&_IF_ORA_10_OR_HIGHER , COUNT(DISTINCT gets) dist_samples
, COUNT(*) total_samples
, COUNT(*) / &_lhp_samples total_samples_pct
FROM
(SELECT /*+ NO_MERGE */ 1 FROM DUAL CONNECT BY LEVEL <= &_lhp_samples) s,
v$latchholder l,
(SELECT
sid indx
, sql_hash_value sqlhash
, sql_address sqladdr
&_IF_ORA_10_OR_HIGHER , sql_child_number sqlchild
&_IF_ORA_10_OR_HIGHER , sql_id sqlid
FROM v$session) s
WHERE
l.sid LIKE '&_lhp_sid'
AND (LOWER(l.name) LIKE LOWER('%&_lhp_name%') OR LOWER(RAWTOHEX(l.laddr)) LIKE LOWER('%&_lhp_name%'))
AND l.sid = s.indx
GROUP BY
&_lhp_what
ORDER BY
total_samples DESC
),
t2 AS (SELECT hsecs FROM v$timer)
SELECT /*+ ORDERED */
&_lhp_what
, s.total_samples
&_IF_ORA_10_OR_HIGHER , s.dist_samples
-- , s.total_samples_pct
, s.total_samples / &_lhp_samples * 100 latchprof_pct_total_samples
, (t2.hsecs - t1.hsecs) * 10 * s.total_samples / &_lhp_samples latchprof_total_ms
-- s.dist_events,
&_IF_ORA_10_OR_HIGHER , (t2.hsecs - t1.hsecs) * 10 * s.total_samples / dist_samples / &_lhp_samples latchprof_avg_ms
FROM
t1,
samples s,
t2
WHERE ROWNUM <= 30
/
COL name CLEAR
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