Download as PDF, PPTX
![blog.tanelpoder.com 10
SQLPLUS
on
Unix
/
Linux
/
MacOS
• Configuration
• Setting
xterm
title
• From
shell
– echo
-‐ne
"033]0;
your
text
here 007”
• From
SQLPLUS
– host
echo
-‐ne
"033]0;
your
text
here 007”
• From
vi
– set
title
– set
titlelen=20
• Decent
terminal
emulators
• Putty
on
Windows
(small,
lightweight
and
works
well!)
– http://www.chiark.greenend.org.uk/~sgtatham/putty/
• Terminator
on
MacOS,
Unix,
Linux
(and
apparently
Windows)
– http://software.jessies.org/terminator/](https://image.slidesharecdn.com/tanelpoderscriptsandtoolsintroshort-151124035615-lva1-app6891/75/Tanel-Poder-Scripts-and-Tools-short-10-2048.jpg)
![blog.tanelpoder.com 16
Setting
up
TPT
scripts
-‐ 2
• Edit
init.sql
(init.sql
sets
up
various
sqlplus
variables)
• Uncomment
the
appropriate
parameters
in
the
SETUP
section
• It
tells
sqlplus
whether
you’re
running
it
on
Windows,
Unix
or
MacOS
-- SETUP SECTION –
-------------------------------------------------------------------
-- Uncomment the following lines if you run your sqlplus on Windows
-------------------------------------------------------------------
-- def SQLPATH=%SQLPATH%
-- def _start=start
-- def _delete=del
-- host doskey /exename=sqlplus.exe desc=set lines 80 sqlprompt ""$Tdescribe $*$Tset lines 299
sqlprompt "SQL> "
-------------------------------------------------------------------
• Edit
i.sql
(i.sql
is
the
“who
am
I”
script
which
also
sets
window
title)
• Uncomment
the
appropriate
title
command
in
the
setup
section
(EOF)
host title &_i_user@&_i_conn [sid=&mysid ser#=&_i_serial spid=&_i_spid …
-- host echo -ne "033]0;&_i_user@&_i_inst sid=&mysid,&_i_serial007"](https://image.slidesharecdn.com/tanelpoderscriptsandtoolsintroshort-151124035615-lva1-app6891/75/Tanel-Poder-Scripts-and-Tools-short-16-2048.jpg)
Uploaded byTanel Poder
Tanel Poder - Scripts and Tools short
The document offers a comprehensive overview of advanced Oracle troubleshooting techniques and tools, specifically focusing on command line setups and SQL*Plus on different operating systems. It discusses configuration, productivity enhancements, command history navigation, and includes scripts for productivity and performance tuning. Additionally, it provides insights into database performance analysis, session activity sampling, and various performance metrics for better diagnosis.
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Tanel Poder - Scripts and Tools short
- 1. blog.tanelpoder.com 1 Advanced Oracle Troubleshooting preparation session: Tanel’s command line setup & tools Tanel Põder http://blog.tanelpoder.com/seminar
- 2. blog.tanelpoder.com 2 Intro: About me • Tanel Põder Oracle Database Performance geek Exadata Performance geek Linux Performance geek Hadoop Performance geek Expert Oracle Exadata book (with Kerry Osborne and Randy Johnson of Enkitec)
- 3. blog.tanelpoder.com 3 All scripts and tools are downloadable and free • Download the scripts and tools from: • http://blog.tanelpoder.com/files/ • Updates (since I delivered this class in 2010): • I have shut the PlanViz website down so ignore some slides • I haven't updated the PerfSheet v3 tool since 2010 • Luca Canali has built a new PerfSheet v4: • http://canali.web.cern.ch/canali/resources.htm
- 4. blog.tanelpoder.com 4 Productivity and speed of action • Talking to Oracle • SQLPLUS still rocks J • …especially in cases where you need to deviate from the usual path • You’ll have a (searchable) history of output of your last commands • On the screen or in a spool/logfile… • You can run your scripts • It’s more “pure” than GUI development tools (which try to be clever, do extra stuff, don’t fetch all data etc)
- 5. blog.tanelpoder.com 5 SQLPLUS on Windows • Configuration • Do NOT use sqlplusw.exe -‐> • This is what you get when running sqlplus from Start menu • Luckily sqlplusw.exe is gone since 11g! • Use CMD.exe and run sqlplus.exe -‐> Much better!!!
- 6. blog.tanelpoder.com 6 • CMD.exe needs some tweaking… • You should check QuickEdit mode, Increase Screen Buffer size etc SQLPLUS on Windows – CMD.exe settings 1. 2. 3.
- 7. blog.tanelpoder.com 7 Setting SQLPLUS Window title automatically • Set cmd window title to include database session info • SQL> host title “test” • @i.sql queries session, instance info from V$ views and sets title accordingly • i.sql is automatically called by login.sql if its in SQLPATH directory
- 8. blog.tanelpoder.com 8 SQLPLUS on Windows • Command line history • Up/Down arrow -‐ navigate between commands • CTRL+Left/Right arrow – jump one word left/right • F7 – Display a popup box with command line history • Use up/down arrows to navigate • ENTER to execute command • Right arrow to put the command to command line for editing • First letter of command to jump between commands starting with that letter (case sensitive) • F8 – Retrieve command from history • Type a beginning of the command (for example “sel”) and press F8 • This will jump through all commands starting with “sel” (case sensitive) • List commands from history • SQL> host doskey /history /exename=sqlplus.exe • @h <text> – history script showing old commands with text int them • @ha – history all
- 9. blog.tanelpoder.com 9 SQLPLUS on Windows • Output formatting • @HTML • Uses SET MARKUP ON HTML • Runs the query in SQLPLUS buffer and spools the output to .HTML file • Launches that .HTML file with appropriate OS command • @XLS • Same as above, but spools to an .XLS file and launches it :-‐) • @CSV • Uses SET COLSEP “,” and spools to a .CSV file
- 10. blog.tanelpoder.com 10 SQLPLUS on Unix / Linux / MacOS • Configuration • Setting xterm title • From shell – echo -‐ne "033]0; your text here 007” • From SQLPLUS – host echo -‐ne "033]0; your text here 007” • From vi – set title – set titlelen=20 • Decent terminal emulators • Putty on Windows (small, lightweight and works well!) – http://www.chiark.greenend.org.uk/~sgtatham/putty/ • Terminator on MacOS, Unix, Linux (and apparently Windows) – http://software.jessies.org/terminator/
- 11. blog.tanelpoder.com 11 SQLPLUS on Unix / Linux / MacOS • Output formatting • Same as on Windows • Launching the HTML file is done with a different command: • MacOS – open command launches the program associated with .HTML extension • Unix/Linux – I just run firefox by default, but you can change it in the script • Terminal with left-‐right scrolling capability? • I’m using Terminator • (Not the one you can install from Ubuntu repositories) • http://software.jessies.org/terminator/ • However, it needs to install its own terminfo file to function properly! – This will be an issue if you need to SSH into a lot of servers in an enterprise – Good for demoing stuff though! J • SQL> set truncate on • Sqlplus allows you to truncate the columns which don’t fit into the linesize instead of wrapping
- 12. blog.tanelpoder.com 12 SQLPLUS on Unix / Linux / MacOS X • Command line history using RLWRAP • Rlwrap (readline wrapper) adds GNU readline capability for any text mode application • BASH shell has the same functionality built in • Just run rlwrap sqlplus instead of just sqlplus (or any other utility) • Rlwrap gives also tab completion! • If you tell it to… • It can use a wordfile (with Oracle keywords, view, column names) – rlwrap -‐f • And it can remember every word it sees on the screen! – rlwrap -‐r
- 13. blog.tanelpoder.com 13 SQLPLUS with RLWRAP – Keyboard shortcuts • Keyboard shortcuts (Emacs mode): • Up/down arrows – navigate command line history • CTRL+A – go to beginning of line • CTRL+E – go to end of line • CTRL+R – search command history backwards • press CTRL+R again to move on to next match • CTRL+S – search command history forward • go “back” from too many CTRL+R’s • ALT+F / ALT+B – Move Forward / Backward by one word • This works if ALT is used as the META key for emacs (check your terminal emulator preferences) • CTRL+K – erase (kill) line from current position to the end of line • CTRL+X, BACKSPACE – erase line from current position to the beginning • CTRL+W or ALT+BACKSPACE – erase one word at a time • CTRL + _ -‐ undo command edit! (or CTRL+X, u)
- 14. blog.tanelpoder.com 14 Installing RLWRAP •Linux • RHEL/OEL/CentOS – Get from here: http://fedoraproject.org/wiki/EPEL • Ubuntu: apt-‐get install rlwrap • MacOS X – Get it from an open source package site for MacOS • MacPorts -‐ http://www.macports.org/ • DarwinPorts -‐ http://darwinports.com/ • Fink -‐ http://www.finkproject.org/ • Solaris (SPARC and Intel) • http://www.sunfreeware.com/ • On HP-‐UX there’s a similar built in command: ied • Should also work on Windows with Cygwin • http://blog.tanelpoder.com/2010/05/07/flexible-‐sqlplus-‐command-‐line-‐history-‐with-‐rlwrap/
- 15. blog.tanelpoder.com 15 Setting up TPT scripts -‐ 1 • Tanel’s Performance Tuning scripts :-‐) • 500+ scripts which I use “every day” • Most scripts do one thing only (such as show parameter values etc) • Also latest versions of the more sophisticated scripts (Snapper, LatchProfX etc) are in there • Download the .zip file and unzip to a directory: • http://blog.tanelpoder.com/files/ • Set SQLPATH variable to point to the script directory • Unix: • export SQLPATH=$HOME/tpt • Windows: • set SQLPATH=C:userstaneltpt • Or Right click on My Computer -‐> Properties -‐> Advanced Settings -‐> Environment Variables; and add it there
- 16. blog.tanelpoder.com 16 Setting up TPT scripts -‐ 2 • Edit init.sql (init.sql sets up various sqlplus variables) • Uncomment the appropriate parameters in the SETUP section • It tells sqlplus whether you’re running it on Windows, Unix or MacOS -- SETUP SECTION – ------------------------------------------------------------------- -- Uncomment the following lines if you run your sqlplus on Windows ------------------------------------------------------------------- -- def SQLPATH=%SQLPATH% -- def _start=start -- def _delete=del -- host doskey /exename=sqlplus.exe desc=set lines 80 sqlprompt ""$Tdescribe $*$Tset lines 299 sqlprompt "SQL> " ------------------------------------------------------------------- • Edit i.sql (i.sql is the “who am I” script which also sets window title) • Uncomment the appropriate title command in the setup section (EOF) host title &_i_user@&_i_conn [sid=&mysid ser#=&_i_serial spid=&_i_spid … -- host echo -ne "033]0;&_i_user@&_i_inst sid=&mysid,&_i_serial007"
- 17.
- 18. blog.tanelpoder.com 18 What is Oracle Database activity about? 1. A bunch of sessions • You need a session for doing anything in Oracle 1. Applications use these sessions to execute (PL)SQL cursors • Any database call requires use of a cursor • Including PL/SQL stored procedure calls 1. The cursor execution will do some work • During the execution, the processes either: • Work on CPU – Or at least want to work on CPU, but OS scheduler doesn’t allow them • Do not Work on CPU – They have been put to sleep by OS because of a blocking system call – They have gone to sleep voluntarily, waiting for some event completion
- 19. blog.tanelpoder.com 19 Sampling session activity details over time – Which SQL? SELECT A SELECT X idle SELECT B UPDATE C Time SID 10 SID 11 SID 12 idle idle SELECT Y INSERT Zidle SELECT N SELECT N UPDATE KSELECT N idle SELECT N SEL SELECT A idle SELECT B UPDATE Cidle idle SELECT Aidle UPDATE C idleidle COMMIT SID 13 SID 14 SID 15 2 x SELECT A 1 x SELECT X 1 x SELECT Y 1 x SELECT N Sample session activity over time -‐> (v$session) 3 x SELECT A 1 x SELECT X 1 x SELECT Y 1 x SELECT N … 3 x UPDATE C 1 x SELECT X 1 x SELECT Y Count the number of (active) sessions each sample, group by SQL ID
- 20. blog.tanelpoder.com 20 Sampling session activity – Working or Waiting? SELECT A SELECT X idle SELECT B UPDATE C Time SID 10 SID 11 SID 12 idle idle SELECT Y INSERT Zidle SELECT N SELECT N UPDATE KSELECT N idle SELECT N SEL SELECT A idle SELECT B UPDATE Cidle idle SELECT Aidle UPDATE C idleidle COMMIT SID 13 SID 14 SID 15 Commit User IO CPU Locks Time Session count
- 21. blog.tanelpoder.com 21 Understanding Database Performance • Performance diagnosis data should have at least these details • Which Sessions? • Which SQL? • Work or wait? • When? • This data can be grouped and summarized by any dimension depending on the “performance question” asked! • The sampled session activity dataset is like a FACT table in DW’s • The existence of a session sample shows that the session was active • The dimension attributes show a large variety of extra details • Which SQL was running, Working or Waiting, Which event, P1,P2.. -‐> v$session.sid -‐> v$session.sql_id, plsql_(sub)program_id -‐> v$session.state, v$session.event, p1,p2,p3 -‐> Time when samples were taken
- 22. blog.tanelpoder.com 22 A selective list of dimensions for performance analysis SQL> desc v$session Name Null? Type ------------------------------- -------- ---------------------------- 1 SADDR RAW(8) 2 SID NUMBER 7 USERNAME VARCHAR2(30) 12 STATUS VARCHAR2(8) 21 PROGRAM VARCHAR2(48) 25 SQL_ID VARCHAR2(13) 37 PLSQL_OBJECT_ID NUMBER 38 PLSQL_SUBPROGRAM_ID NUMBER 39 MODULE VARCHAR2(48) 41 ACTION VARCHAR2(32) 45 ROW_WAIT_OBJ# NUMBER 61 CLIENT_IDENTIFIER VARCHAR2(64) 64 BLOCKING_SESSION NUMBER 70 EVENT VARCHAR2(64) 71 P1TEXT VARCHAR2(64) 72 P1 NUMBER 74 P2TEXT VARCHAR2(64) 75 P2 NUMBER 77 P3TEXT VARCHAR2(64) 78 P3 NUMBER 82 WAIT_CLASS VARCHAR2(64) 85 STATE VARCHAR2(19) Status is ACTIVE for sessions running a database call (background sessions are always in a call) Easy way to get TOP SQL, just group and count the samples by SQL_ID From 10.2.0.3 onwards you can get easy TOP PL/SQL, just group by PL_SQL_OBJECT_ID/SUBP ROGRAM_ID and join to same columns in DBA_PROCEDURES Very important to remember: If wait STATE != WAITING, the session is NOT WAITING (It’s working on CPU or tries to get onto CPU) If you want the TOP BLOCKER, just group the samples by blocking_session For TOP WAITs, just group the samples by EVENT where STATE=WAITING
- 23. blog.tanelpoder.com 23 Instance Activity overview • What is the database (instance) doing right now? • @a.sql – Instance Activity SQL • It takes one ASH style sample of V$SESSION and shows TOP sql/wait • I wrote it to show how easy it is to get an overview of instance activity • But it’s also very short to type – I actually use it regularly :-‐) • I just run it couple of times in a row! select count(*) , sql_id , case state when 'WAITING' then 'WAITING' else 'ON CPU' end state , case state when 'WAITING' then event else 'On CPU / runqueue' end event from v$session where status='ACTIVE’ and wait_class != 'Idle' and sid != (select sid from v$mystat where rownum=1) group by sql_id , case state when 'WAITING' then 'WAITING' else 'ON CPU' end , case state when 'WAITING' then event else 'On CPU / runqueue' end order by count(*) desc
- 24. blog.tanelpoder.com 24 Snapper -‐Overview • Major improvement – ASH style session activity sampling! • From V$SESSION / V$SESSION_WAIT (no separate licenses needed) • @snapper ash <total_seconds> <sampling_interval> <SIDs> • Still works all the way from Oracle 9.2 to latest Oracle version • Still NO installation/database changes are needed! • It’s just an anonymous PL/SQL block, parsed on the fly… • Look into the code to see some cool challenges involved!!! • Still free and still has a picture of a real Snapper (fish) in it! ;-‐) • …and you can still run it directly from web if you feel adventurous • SQL> @http://blog.tanelpoder.com/files/scripts/snapper.sql .....
- 25. blog.tanelpoder.com 25 Snapper –Session Activity Sampling • Example 1a: Single Session troubleshooting: SQL> @snapper ash,gather=n 5 1 32 -- Session Snapper v3.01 by Tanel Poder ( http://www.tanelpoder.com ) ------------------------------- Sampled Session Activity Profile ----------------------- -- Act% | Wait Event | Wait Class | SQL_ID -- ---------------------------------------------------------------------------------------- 84% | db file scattered read | User I/O | g723q6scvr9h8 11% | ON CPU | ON CPU | g723q6scvr9h8 3% | db file sequential read | User I/O | 3% | ON CPU | ON CPU | c0j6cx9kzjf7g SQL> @sqlid g723q6scvr9h8 HASH_VALUE CH# SQL_TEXT ---------- ---- ----------------------------------------------------------------------- 431728136 0 /* SQL Analyze(0) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) dbms_stats cursor_sharing_exact use_weak_name_resl dynamic_sampling(0) no_monitoring no_substrb_pad */to_char(count ("SYS_NC00009$")),to_char(substrb(dump(min("SYS_NC00009$"),16,0,32), As we measure a single session, then the max Activity% can be 100% (allow for some rounding errors). If the activity is measured less than 100%, it means that the session was not active the remaining time (it was idle).
- 26. blog.tanelpoder.com 26 Snapper –Session Activity and Performance Counters • Example 1b: Single Session troubleshooting with perf counters SQL> @snapper ash,stats 5 1 146 -- Session Snapper v3.01 by Tanel Poder ( http://www.tanelpoder.com ) -------------------------------------------------------------------------------------------------------- SID, USERNAME , TYPE, STATISTIC , DELTA, HDELTA/SEC, %TIME, -------------------------------------------------------------------------------------------------------- 146, SYS , STAT, session logical reads , 309970, 61.99k, 146, SYS , STAT, consistent gets , 309966, 61.99k, 146, SYS , STAT, consistent gets from cache , 309967, 61.99k, 146, SYS , STAT, consistent gets from cache (fastpath) , 309968, 61.99k, 146, SYS , STAT, calls to kcmgcs , 1660, 332, 146, SYS , STAT, no work - consistent read gets , 308388, 61.68k, 146, SYS , STAT, table scans (short tables) , 332, 66.4, 146, SYS , STAT, table scan rows gotten , 25006755, 5M, 146, SYS , STAT, table scan blocks gotten , 308415, 61.68k, 146, SYS , TIME, DB CPU , 3960000, 792ms, 79.2% 146, SYS , TIME, sql execute elapsed time , 4059947, 811.99ms, 81.2% 146, SYS , TIME, DB time , 4059947, 811.99ms, 81.2% -- End of snap 1, end=2010-03-01 11:31:10, seconds=5 ---------------------------------- Sampled Session Activity Profile ------------------------------ -- Act% | Wait Event | Wait Class | SQL_ID -- -------------------------------------------------------------------------------------------------- 100% | ON CPU | ON CPU | 7vxd09448zcrx
- 27. blog.tanelpoder.com 27 Snapper –Session Activity Sampling • Example 2: Whole instance overview • You can write any query instead of the list of SIDs: SQL> @snapper ash,stats,gather=n 30 1 "select sid from v$session" -- Session Snapper v3.01 by Tanel Poder ( http://www.tanelpoder.com ) ------------------- Sampled Session Activity Profile ---------------------------- -- Act% | Wait Event | Wait Class | SQL_ID -- --------------------------------------------------------------------------------- 164% | read by other session | User I/O | 3jbwa65aqmkvm 99% | ON CPU | ON CPU | 7vxd09448zcrx 99% | ON CPU | ON CPU | bt4txmkqf7u89 98% | db file scattered read | User I/O | 3jbwa65aqmkvm 98% | direct path read | User I/O | 3jbwa65aqmkvm 61% | db file scattered read | User I/O | dw2zgaapax1sg 41% | control file parallel wri | System I/O 34% | db file async I/O submit | System I/O 27% | log file parallel write | System I/O 24% | db file sequential read | User I/O | 0bzhqhhj9mpaa As we are measuring more than one session, then it’s ok to see over 100% of activity. 100% stands for all response time of a single session!
- 28. blog.tanelpoder.com 28 Snapper –Performance Counters • Example 3a -‐ Find top REDO geneators SQL> @snapper ash,stats,gather=s,sinclude=redo_size 5 1 "select sid from v$session” -- Session Snapper v3.01 by Tanel Poder ( http://www.tanelpoder.com ) ------------------------------------------------------------------------------------------------ SID, USERNAME , TYPE, STATISTIC , DELTA, HDELTA/SEC, ------------------------------------------------------------------------------------------------ 20, SYS , STAT, redo size , 13376076, 2.68M, 31, SYS , STAT, redo size , 18232, 3.65k, 143, SYS , STAT, redo size , 26796, 5.36k, -- End of snap 1, end=2010-03-01 11:52:47, seconds=5 --------------------------------- Sampled Session Activity Profile ----------------------------- -- Act% | Wait Event | Wait Class | SQL_ID -- ------------------------------------------------------------------------------------------------ 69% | log file parallel write | System I/O 50% | ON CPU | ON CPU | crwqs334cz65x 27% | log buffer space | Configuration | crwqs334cz65x 12% | log buffer space | Configuration | f6f6wxb0st0yp 8% | ON CPU | ON CPU 8% | db file sequential read | User I/O | gvt8zu1k1tsff
- 29. blog.tanelpoder.com 29 Snapper –Performance Counters • Example 3b: • Find top IO throughput (MB) users SQL> @snapper stats,gather=s,sinclude=physical%bytes 5 1 "select sid from v$session" -- Session Snapper v3.01 by Tanel Poder ( http://www.tanelpoder.com ) ----------------------------------------------------------------------------------------------- SID, USERNAME , TYPE, STATISTIC , DELTA, HDELTA/SEC, ----------------------------------------------------------------------------------------------- 6, (CKPT) , STAT, physical read total bytes , 16384, 3.28k, 6, (CKPT) , STAT, physical write total bytes , 32768, 6.55k, 6, (CKPT) , STAT, cell physical IO interconnect bytes , 49152, 9.83k, 20, SYS , STAT, physical read total bytes , 29360128, 5.87M, 20, SYS , STAT, cell physical IO interconnect bytes , 29360128, 5.87M, 20, SYS , STAT, physical read bytes , 29360128, 5.87M, 139, SOE , STAT, physical read total bytes , 1835008, 367k, 139, SOE , STAT, cell physical IO interconnect bytes , 1835008, 367k, 139, SOE , STAT, physical read bytes , 1835008, 367k, -- End of snap 1, end=2010-03-01 12:00:35, seconds=5 • You can use the same trick with any performance counter • IOPS – @snappiops • CPU – @snapcpu
- 30. blog.tanelpoder.com 30 Snapper –Write output to a tracefile • Example 4: • SQL> @snapper ash,trace 30 999999 all • Uses DBMS_SYSTEM.KSDWRT() for writing to the tracefile • In above example, a Snapper snapshot is written to a tracefile every 30 seconds (and 999999 times in a row unless you cancel) • You can run tail -‐f in OS for realtime Snapper output monitoring • “all” option instead of a SID stands for all sessions in the database • Note that gathering V$SESSTAT stats for a lot of sessions frequently is CPU-‐ expensive • That’s why the “all” option disables V$SESSTAT gathering in Snapper v3.0 by default • You can still enable it by adding the gather=… option to collect the stats you want (read the script header for documentation)
- 31. blog.tanelpoder.com 31 Snapper –Advanced Performance Counters • 1178 V$SESSTAT performance counters in Oracle 12.1.0.2! • One separate set for each session! • Where are the performance counters documented? • Oracle Database Reference – “Statistics Descriptions” • http://download.oracle.com/docs/cd/E14072_01/server.112/e10820/stats002.htm • Note that the above URL may change when Oracle releases new docs
- 32. blog.tanelpoder.com 32 Case study – Bad index build performance -‐ 1 • An index build was taking too long time • Function based index build on a busy table • Build, not re-‐build • Ran with ONLINE option • Executed in parallel • The parallel slaves were doing the full table scan • But they were waiting for db file sequential read for over 80% of their time • Why would be the parallel slaves (which did a full table scan) be doing single block reads so much?
- 33. blog.tanelpoder.com 33 Case study – Bad index build performance -‐ 2 --------------------------------------------------------------------------------- -- SID, TYPE, STATISTIC , DELTA, HDELTA/SEC --------------------------------------------------------------------------------- 3768, STAT, session logical reads , 11522, 677.76 3768, STAT, physical read total IO requests , 4188, 246.35 3768, STAT, physical read total multi block requests, 877, 51.59 3768, STAT, physical read total bytes , 73924608, 4.35M 3768, STAT, consistent gets , 11559, 679.94 3768, STAT, consistent gets from cache , 11556, 679.76 3768, STAT, consistent gets - examination , 615, 36.18 3768, STAT, physical reads , 8988, 528.71 3768, STAT, physical reads cache , 8988, 528.71 3768, STAT, physical read IO requests , 4197, 246.88 3768, STAT, physical read bytes , 73637888, 4.33M 3768, STAT, physical reads cache prefetch , 4752, 279.53 3768, STAT, table scan rows gotten , 28079, 1.65k 3768, STAT, table scan blocks gotten , 7399, 435.24 3768, STAT, table fetch continued row , 3335, 196.18 3768, STAT, PX local messages sent , 192, 11.29 3768, WAIT, db file sequential read , 14393221, 846.66ms 3768, WAIT, db file scattered read , 1040277, 61.19ms Total single block IO requests = total IO requests – total multi block requests = 246 – 51 = 195 physical reads is a misleading name – it’s really the number of blocks read via PIOs single block reads due chained / migrated rows!
- 34. blog.tanelpoder.com 34 Snapper -‐Summary • Oracle Session Snapper is a powerful ad-‐hoc session-‐level performance diagnosis tool which does not require any installation or database changes! • Features: • ASH style session activity sampling • Reports top SQL, top Waits, etc • Very useful for drilling down to details when the plain wait interface and SQL trace do not give enough details • Takes snapshots of V$ views (V$SESSTAT, etc) and reports deltas • Report all stats of some sessions (like the advanced diagnosis example) • Report some stats of all sessions (like the redo or IO example) • Flexible!