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Олег Коротков korotkov@devexperts.com

Олег Коротков korotkov@devexperts.com. AWR, ASH - use cases and 11.2 enhancements. Олег Коротков korotkov@devexperts.com. Agenda. - Automatic Workload Repository (AWR) - Basic ideas - dba_hist % views - 11.2 enhancements - AWR use cases & limitations

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Олег Коротков korotkov@devexperts.com

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  1. Олег Коротков korotkov@devexperts.com AWR, ASH - use cases and 11.2 enhancements

  2. Олег Коротков korotkov@devexperts.com Agenda - Automatic Workload Repository (AWR) - Basic ideas - dba_hist% views - 11.2 enhancements - AWR use cases & limitations - Active Session History (ASH) - Basic ideas - 11.2 enhancements - Typical use cases

  3. Олег Коротков korotkov@devexperts.com Agenda - Automatic Workload Repository (AWR) - Basic ideas - dba_hist% views - 11.2 enhancements - AWR use cases & limitations - Active Session History (ASH) - Basic ideas - 11.2 enhancements - Typical use cases

  4. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Oracle Database performance diagnostics tools evolution: - UTLBSTAT/UTLESTAT - STATSPACK (starting from Oracle 8i) - AWR (starting from Oracle 10g) But the idea is the same…

  5. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Oracle has a lot of operational statistics/metrics gathered since the instance startup.

  6. Олег Коротков korotkov@devexperts.com Automatic Workload Repository SQL> select inst_id, name, value from gv$sysstat where name in ('physical reads','session logical reads','usercommits','user rollbacks') order by name, inst_id; INST_ID NAME VALUE ---------- ---------------------- ---------- 1 physical reads 219525005 2 physical reads 905189162 1 session logical reads 5925054313 2 session logical reads 1.7457E+10 1 user commits 5294595 2 user commits 28113236 1 user rollbacks 8455066 2 user rollbacks 150792358 -- All stattistics: select * from v$statname; 10.2.0.4 = 387; 10.2.0.5 = 395 11.2.0.2 = 628

  7. Олег Коротков korotkov@devexperts.com Automatic Workload Reports SQL> select inst_id, event, total_waits, time_waited, average_wait, sum(time_waited_micro) over (partition by event) twm_total from gv$system_event where wait_class='User I/O' order by twm_totaldesc, event, inst_id; INST_ID EVENT TOTAL_WAITS TIME_WAITED AVERAGE_WAIT TWM_TOTAL ---------- ------------------------- ----------- ----------- ------------ ---------- 1 db file sequential read 27577537 40274551 1.46 3.8091E+12 2 db file sequential read 159856155 340633564 2.13 3.8091E+12 1 direct path read temp 44837941 8919281 .2 2.9431E+11 2 direct path read temp 122808964 20511343 .17 2.9431E+11 1 direct path read 1435296 1511142 1.05 9.9823E+10 2 direct path read 12075539 8471152 .7 9.9823E+10 -- All events: select count(*) from v$event_name; 10.2.0.4 = 889; 10.2.0.5 = 916 11.2.0.2 = 1142

  8. Олег Коротков korotkov@devexperts.com Automatic Workload Repository SQL> select sql_id, execs, rw, LIOs, PhIOs from ( 2 select sql_id, /*sql_text,*/ sum(executions) execs, 3 sum(rows_processed) rw, sum(buffer_gets) LIOs, sum(disk_reads) PhIOs 4 from gv$sql 5 where module='SQL Developer' and rownum>=1 6 group by sql_id/*, sql_text*/ 7 order by PhIOsdesc) 8 where rownum<=5; SQL_ID EXECS RW LIOS PHIOS ------------- ---------- ---------- ---------- ---------- 3w1fk8r93360m 1 1 8156 348 davt444np8yr7 6 6 3583 289 7b775q3tc69a9 22 22 2899 213 58kz178ugwm87 29 29 2982 96 ayaq4d3bbt7k8 1 3 106 88

  9. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR just makes a copy of system views with scheduled time interval… … and gives a possibility to make a report (diff) based on two snapshots. gv$sysstat gv$sysstat DB activity [8AM, 9AM] gv$system_event gv$system_event Snap at 8 AM; done by MMON Snap at 9 AM gv$sql gv$sql … …

  10. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR configuration. - Oracle Diagnostic Pack is required (Oracle EE additional option). - STATISTICS_LEVEL = TYPICAL or ALL - (11g) CONTROL_MANAGEMENT_PACK_ACCESS = DIAGNOSTIC or DIAGNOSTIC+TUNING

  11. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR configuration. SQL> select * from dba_hist_wr_control; DBID SNAP_INTERVAL RETENTION TOPNSQL ---------- ------------------ ------------------ ---------- 1486911308 +00000 01:00:00.0 +00007 00:00:00.0 DEFAULT To change: dbms_workload_repository.modify_snapshot_settings( retention=>129600, -- New retention time (in minutes). 60*24*90=129600 interval=>30, -- New interval setting between each snapshot, in units of minutes topnsql=>50 – Number 30..50000; 'DEFAULT', 'MAXIMUM' )

  12. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Create (additional) snapshot: dbms_workload_repository.create_snapshot('ALL') -- flush_level = 'TYPICAL' or 'ALL‘ SQL> select dbms_workload_repository.create_snapshot from dual; CREATE_SNAPSHOT --------------- 7762 SQL> select dbms_workload_repository.create_snapshot('ALL') from dual; DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT('ALL') ----------------------------------------------- 7763 SQL> select snap_id, count(*) from dba_hist_sqlstat where snap_id in (7762,7763) group by snap_id; SNAP_ID COUNT(*) ---------- ---------- 7763 103 7762 59

  13. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Generate report across two snapshots: select * from table( dbms_workload_repository.awr_report_text( 2334238573, -- DBID 1, -- instance number 38392, -- ‘Begin Snapshot’ ID 38393, -- ‘End Snapshot’ ID 0) -- flag = 0 or 8 (display ADDM specific parts) ); -- ADDM sections: Buffer Cache Advisory (for ADDM); SGA Target Advisory (for ADDM); Shared Pool Advisory (for ADDM); Streams Pool Advisory (for ADDM); PGA Target Advisory (for ADDM) There is a similar awr_report_html() function.

  14. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR report (fragments) 1/8: WORKLOAD REPOSITORY report for DB Name DB Id Instance Inst Num Startup Time Release RAC ------------ ----------- ------------ -------- --------------- ----------- --- XXXXX 207063651 ###### 1 09-Oct-11 20:43 11.2.0.2.0 YES Host Name Platform CPUs Cores Sockets Memory(GB) ---------------- -------------------------------- ---- ----- ------- ---------- ###### Linux x86 64-bit 8 8 4 31.38 Snap Id Snap Time Sessions Curs/Sess --------- ------------------- -------- --------- Begin Snap: 46095 03-Feb-12 08:00:02 248 5.0 End Snap: 46096 03-Feb-12 09:00:12 249 5.0 Elapsed: 60.17 (mins) DB Time: 183.68 (mins) 11.2 new data/format

  15. Олег Коротков korotkov@devexperts.com Automatic Workload Reports AWR reports 2/8: Load Profile Per Second Per Transaction Per Exec Per Call ~~~~~~~~~~~~ --------------- --------------- ---------- ---------- DB Time(s): 3.1 0.4 0.05 0.02 DB CPU(s): 1.1 0.1 0.02 0.01 Redo size: 167,379.4 20,585.9 Logical reads: 70,689.2 8,694.0 Block changes: 769.8 94.7 Physical reads: 3,480.6 428.1 Physical writes: 126.5 15.6 User calls: 138.9 17.1 Parses: 46.4 5.7 Hard parses: 0.1 0.0 W/A MB processed: 4.9 0.6 Logons: 0.1 0.0 Executes: 63.2 7.8 Rollbacks: 0.3 0.0 Transactions: 8.1

  16. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR report 3/8: Top 5 Timed Foreground Events ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Avg wait % DB Event Waits Time(s) (ms) time Wait Class ------------------------------ ------------ ----------- ------ ------ ---------- db file sequential read 618,214 4,667 8 42.3 User I/O DB CPU 4,085 37.1 direct path read temp 810,891 1,726 2 15.7 User I/O enq: TX - row lock contention 693 208 300 1.9 Applicatio log file sync 29,137 104 4 .9 Commit Host CPU (CPUs: 8 Cores: 8 Sockets: 4) ~~~~~~~~ Load Average Begin End %User %System %WIO %Idle --------- --------- --------- --------- --------- --------- 4.45 4.17 27.9 1.1 14.1 70.7 Instance CPU ~~~~~~~~~~~~ % of total CPU for Instance: 15.0 % of busy CPU for Instance: 51.3

  17. Олег Коротков korotkov@devexperts.com Automatic Workload Reports AWR reports 4/8: Wait Event Histogram DB/Inst: ######/###### Snaps: 46095-46096 <…> % of Waits ----------------------------------------------- Total Event Waits <1ms <2ms <4ms <8ms <16ms <32ms <=1s >1s -------------------------- ----- ----- ----- ----- ----- ----- ----- ----- ----- db file sequential read 619.1 22.0 1.8 9.4 37.0 25.0 3.5 1.5 .0 <…> Waits 64ms Event to 2s <32ms <64ms <1/8s <1/4s <1/2s <1s <2s >=2s -------------------------- ----- ----- ----- ----- ----- ----- ----- ----- ----- db file sequential read 9020 98.5 1.0 .3 .1 .1 .0 .0 .0 <…> Waits 4s Event to 2m <2s <4s <8s <16s <32s < 1m < 2m >=2m -------------------------- ----- ----- ----- ----- ----- ----- ----- ----- ----- db file sequential read 1 100.0 .0

  18. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR report 5/8: SQL ordered by Elapsed Time DB/Inst: ######/##### Snaps: 46095-46096 <…> Elapsed Elapsed Time Time (s) Executions per Exec (s) %Total %CPU %IO SQL Id ---------------- -------------- ------------- ------ ------ ------ ------------- 3,610.8 4 902.69 32.8 3.8 96.6 3c8sz91kt214t Module: JDBC Thin Client MERGE INTO … 3,609.9 0 N/A 32.8 52.0 47.8 0q694rv7gzkzs Module: SQL*Plus SELECT count(*) FROM …

  19. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR report 6/8: SQL ordered by Elapsed Time SQL ordered by CPU Time SQL ordered by User I/O Wait Time SQL ordered by Gets SQL ordered by Reads SQL ordered by Physical Reads (UnOptimized) -> UnOptimized Read Reqs = Physical Read Reqts - Optimized Read Reqs SQL ordered by Executions SQL ordered by Parse Calls SQL ordered by Sharable Memory SQL ordered by Version Count SQL ordered by Cluster Wait Time

  20. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR report 7/8: IOStat by Function summary DB/Inst: #####/##### Snaps: 46095-46096 Reads: Reqs Data Writes: Reqs Data Waits: Avg Function Name Data per sec per sec Data per sec per sec Count Tm(ms) --------------- ------- ------- ------- ------- ------- ------- ------- ------- Direct Reads 45.5G 228.3 12.9145 0M 0.0 0M 0 N/A Buffer Cache Re 2.4G 171.7 .681144 0M 0.0 0M 619.1K 7.1 DBWR 0M 0.0 0M 1.7G 71.4 .493891 0 N/A <…> TOTAL: 48.9G 409.7 13.8572 2.8G 89.3 .800808 716.7K 6.3 IOStat by Filetype summary DB/Inst: #####/##### Snaps: 46095-46096 Reads: Reqs Data Writes: Reqs Data Small Large Filetype Name Data per sec per sec Data per sec per sec Read Read --------------- ------- ------- ------- ------- ------- ------- ------- ------- Temp File 39.6G 224.9 11.2232 0M 0.0 0M 1.6 N/A Data File 8.4G 175.2 2.37223 1.7G 71.4 .493060 7.1 29.1 <…> TOTAL: 48.9G 409.7 13.8569 2.8G 89.3 .799977 3.9 31.7 IOStat by Function/Filetype summary

  21. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR report 8/8: Segments by Physical Reads Segments by Physical Read Requests Segments by UnOptimized Reads Segments by Optimized Reads Segments by Direct Physical Reads Segments by Physical Writes Segments by Physical Write Requests Segments by Direct Physical Writes Segments by Table Scans Segments by DB Blocks Changes + enhanced RAC (interconnect, DRM) statistics

  22. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Other AWR reports/procedures: Dbms_workload_repository package: ASH_report_text (ASH_report_html) ASH_global_report_text AWR_diff_report_text AWR_global_diff_report_text AWR_global_report_text AWR_SQL_report_text Dbms_xplan.display_awr

  23. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR baselines. Baseline is a pair of snapshots… Oracle10g: fixed baselines only: DBMS_WORKLOAD_REPOSITORY.CREATE_BASELINE( start_snap_id, end_snap_id, baseline_name... ); Oracle 11g: baseline templates for fixed date or for repeated timeframe.

  24. Олег Коротков korotkov@devexperts.com Automatic Workload Repository AWR tables and views. AWR data is stored in SYS schema in SYSAUX tablespace. Looks like there are WRH$% and WRM$% tables. DBA_HIST% views are created above the tables. 10.2.0.4 – 78 views; 11.2.0.2 – 111 views

  25. Олег Коротков korotkov@devexperts.com Automatic Workload Repository select <...> from dba_hist_snapshot, dba_hist_sys_time_model <...> Date min_snap_idmax_id DB time DB CPU 31.01.2012 121851 121955 3582,46 1899,31 30.01.2012 121747 121850 3942,73 1787,58 29.01.2012 121643 121746 3225,62 1587,83 28.01.2012 121538 121642 2626,14 1410,22 27.01.2012 121435 121537 -705799,94 -284112,92 26.01.2012 121329 121434 3524,76 1934,44 25.01.2012 121226 121328 3935,66 2004,01

  26. Олег Коротков korotkov@devexperts.com Automatic Workload Repository select <...> from dba_hist_snapshot, dba_hist_system_event <...> Event_name waits_1 duration_1 waits_2 duration_2 gc buffer busy 1378135 1,9 16189 0,4 gccr grant 2-way 5830652 0,2 97805 0,2 gc current block 2-way 2783997 0,3 365330 0,3 gccr multi block request 1339350 0,2 1850738 0,2 gccr block 2-way 39967 0,3 948740 0,3 gc current grant busy 298901 0,7 20273 0,3 gc current grant 2-way 1027710 0,2 1164 0,3

  27. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Example 1. Average and Skew. So four executions took 278 seconds (69,5*4). How long did each take? 69,5 in average.

  28. Олег Коротков korotkov@devexperts.com Automatic Workload Repository select <...> from dba_hist_snapshot, dba_hist_sqlstat <...> SNAP_ID EXECS ELA GETS READS IOWAIT PLAN_HASH_VALUE ---------- ---------- ---------- ---------- ---------- ---------- --------------- 4918 1 178966 45213 0 0 4196013364 4876 1 1145258 151525 34 599518 4196013364 4854 1 1775405 114964 127 1277256 4196013364 4770 1 274975901 3775568 21750 260995652 4196013364 69,5 in average. But no any execution even close to this time.

  29. Олег Коротков korotkov@devexperts.com Automatic Workload Repository Example 2. TOPNSQL. A query is the same (9g7dr4k9qj1r1). Usage pattern is the same. “Heavy” executions: DD EXECS ELA_PER_EXEC GETS_PER_EXEC -------------------- ---------- ------------ ------------- 28.12.2011 14 1053 379809 21161 28.12.2011 13 12336 9043237 21148 28.12.2011 12 942 379609 21296 28.12.2011 11 1097 378855 21060 28.12.2011 10 1505 382856 21168 28.12.2011 09 6102 7229608 21604 “Light” executions: -------------------- ---------- ------------ ------------- 29.12.2011 14 5860 2003 89 29.12.2011 13 6723 2016 91 29.12.2011 10 6435 2008 86 There were no executions in some snaps. ADD_COLORED_SQL/REMOVE_COLORED_SQL to mark sql_id.

  30. Олег Коротков korotkov@devexperts.com Automatic Workload Repository A kind of conclusion about AWR. - It’s very useful tool for analyzing performance in past periods. - Oracle11g AWR is better (more comprehensive and more convenient) than 10g. - Selecting from AWR views gives even more powerful and flexible reports. But… AWR requires addition licensing. It gives you only aggregated information. Some data can be ‘omitted’.

  31. Олег Коротков korotkov@devexperts.com Agenda - Automatic Workload Repository (AWR) - Basic ideas - dba_hist% views - 11.2 enhancements - AWR use cases & limitations - Active Session History (ASH) - Basic ideas - 11.2 enhancements - Typical use cases

  32. Олег Коротков korotkov@devexperts.com Active Session History Active Session History (ASH) is a new tool introduced in Oracle10g. Once a second it makes snapshot of active sessions (on CPU or in non-Idle events). Something close to… select ... from gv$session where wait_class<>'Idle'; ASH data is not complete but.. It is not aggregated(like other AWR data).

  33. Олег Коротков korotkov@devexperts.com Active Session History dba_hist_active_sess_history 10.2.0.5 – 52 columns; 11.2.0.2 – 97 columns. Some of the columns: SNAP_ID, DBID, INSTANCE_NUMBER, SAMPLE_ID, SAMPLE_TIME – sample identification; SESSION_ID, SESSION_SERIAL#, USER_ID, PROGRAM, MODULE, MACHINE, PORT –session identification; SQL_ID, SQL_PLAN_HASH_VALUE, SQL_PLAN_LINE_ID, SQL_EXEC_ID – SQL information; EVENT, P1, P2, P3, TIME_WAITED – wait event information; BLOCKING_SESSION, BLOCKING_SESSION_SERIAL#, BLOCKING_INST_ID – locking information; TM_DELTA_CPU_TIME, TM_DELTA_DB_TIME, DELTA_READ_IO_REQUESTS. DELTA_WRITE_IO_REQUESTS, DELTA_READ_IO_BYTES, DELTA_WRITE_IO_BYTES, DELTA_INTERCONNECT_IO_BYTES – session activity info.

  34. Indexed on time Readers go unlatched Readers go the opposite way Writer goes one direction Олег Коротков korotkov@devexperts.com Agenda V$SESSION V$SESSION_WAIT DBA_HIST_ACTIVE_SESS_HISTORY V$ACTIVE_SESSION_HISTORY ASH architecture (John Beresniewicz. Practical Active Session History) Write 1 out of 10 samples Session state objects AWR Circular bufferin SGA (2MB per CPU) MMON Lite(MMNL) Every second Every hour (or flush) Direct-path INSERTS

  35. Олег Коротков korotkov@devexperts.com Active Session History ASH in memory – fixed memory consumption, variable time range. SQL> select inst_id, bytes/(1024*1024) MB from gv$sgastat where name='ASH buffers'; INST_ID MB ---------- ---------- 1 16 3 16 2 16 SQL> select inst_id, (max(sample_time)-min(sample_time)) ASH_window from gv$active_session_history group by inst_id; INST_ID ASH_WINDOW ---------- ------------------------------- 1 +000000000 07:18:12.038 2 +000000000 07:01:26.268 3 +000000000 10:15:25.558 Samples for every second.

  36. Олег Коротков korotkov@devexperts.com Active Session History ASH on disk – fixed time range controlled by AWR retention. SQL> select instance_number, (max(sample_time)-min(sample_time)) ASH_window from dba_hist_active_sess_history group by instance_number; INSTANCE_NUMBER ASH_WINDOW --------------- ---------------------------------- 1 +000000032 04:59:50.479 2 +000000032 04:59:45.743 3 +000000032 04:59:40.818 SQL> select 'ASH in memory' what, count(distinct sample_id) samples_per_hour 2 from v$active_session_history 3 where sample_time>=trunc(sysdate) and sample_time<trunc(sysdate)+1/24 4 union all 5 select 'ASH on disk', count(distinct sample_id) sample_id 6 from dba_hist_active_sess_history 7 where instance_number=1 and sample_time>=trunc(sysdate) and sample_time<trunc(sysdate)+1/24; WHAT SAMPLES_PER_HOUR ------------- ---------------- ASH in memory 3592 ASH on disk 359 1/10 of samples from ‘ASH in memory’.

  37. Олег Коротков korotkov@devexperts.com Active Session History Each sample in ASH data represents a second of database activity. Theoretically: - Number of rows for one sample is DB Time. - Number of rows with session_state=‘ON CPU’ is DB CPU. In my experience the accuracy of the calculation hardly ever better than 15-20% on production systems with significant load.

  38. Олег Коротков korotkov@devexperts.com Active Session History Example 1. AWR report: Snap Id Snap Time Sessions Curs/Sess --------- ------------------- -------- --------- Begin Snap: 118264 27-Dec-11 13:30:23 1,410 49.8 Elapsed: 15.06 (mins) DB Time: 2,438.18 (mins) <…> Event Waits Time (s) (ms) Time Wait Class ------------------------------ ------------ ----------- ------ ------ ---------- latch: cache buffers chains 409,488 51,930 127 35.5 Concurrenc CPU time 6,341 4.3 db file sequential read 164,900 1,113 7 0.8 User I/O <…> Elapsed CPU Elap per % Total Time (s) Time (s) Executions Exec (s) DB Time SQL Id ---------- ---------- ------------ ---------- ------- ------------- 139,282 4,307 11,574 12.0 95.2 9g7dr4k9qj1r1 140 000 (ela for the query) / 900 (15 minutes) = = 155concurrently executed queries.

  39. Олег Коротков korotkov@devexperts.com Active Session History Example 1. ASH content (1/3): SQL> select to_char(trunc(sample_time,'mi'),'hh24:mi') dd, count(*) c, 2 count(distinct h.session_id||':'||h.session_serial#) s 3 from dba_hist_active_sess_history h 4 where h.instance_number=1 and h.snap_id between 118265 and 118265 5 and h.sample_time>=to_date('27.12.2011 13:30','dd.mm.yyyy hh24:mi') 6 and h.sample_time <to_date('27.12.2011 13:45','dd.mm.yyyy hh24:mi') 7 group by trunc(sample_time,'mi') order by trunc(sample_time,'mi'); DD C S --------------- ---------- ---------- 13:30 33 24 13:31 3134 1044 13:32 4846 914 13:33 55 48 13:34 37 24 13:35 28 17 13:36 25 17 13:37 239 230 13:38 5242 1016 13:39 1188 873 13:40 28 26 13:41 19 19 <…>

  40. Олег Коротков korotkov@devexperts.com Active Session History Example 1. ASH content (2/3): SQL> select sample_time, count(*) c, 2 sum(case when sql_id='9g7dr4k9qj1r1' then 1 else 0 end) s 3 from dba_hist_active_sess_history h 4 where h.instance_number=1 and h.snap_id between 118265 and 118265 5 and h.sample_time>=to_date('27.12.2011 13:30','dd.mm.yyyy hh24:mi') 6 and h.sample_time <to_date('27.12.2011 13:45','dd.mm.yyyy hh24:mi') 7 group by sample_time order by sample_time; …

  41. Олег Коротков korotkov@devexperts.com Active Session History Example 1. ASH content (3/3): SAMPLE_TIME C S ------------------------------ ---------- ---------- 27-DEC-11 01.30.05.551 PM 6 0 27-DEC-11 01.30.15.591 PM 5 0 <…> 27-DEC-11 01.31.15.850 PM 4 0 27-DEC-11 01.31.25.959 PM 410 395 27-DEC-11 01.31.36.069 PM 980 963 27-DEC-11 01.31.46.652 PM 887 857 27-DEC-11 01.31.56.951 PM 848 822 27-DEC-11 01.32.06.994 PM 862 844 27-DEC-11 01.32.17.056 PM 852 831 27-DEC-11 01.32.27.118 PM 869 842 27-DEC-11 01.32.37.165 PM 855 840 27-DEC-11 01.32.47.225 PM 800 776 27-DEC-11 01.32.57.516 PM 608 570 27-DEC-11 01.33.07.566 PM 25 10 27-DEC-11 01.33.17.613 PM 8 1 27-DEC-11 01.33.27.658 PM 5 1 27-DEC-11 01.33.37.690 PM 4 0 <…>

  42. Олег Коротков korotkov@devexperts.com Active Session History Example 2. sql_exec_id (Oracle 11g) (1/2). SQL_EXEC_ID is counter of SQL executions on a given instance. (See TanelPoder blog entry.) SQL> declare j number; begin dbms_job.submit(job=>j, what=>'declare p number; begin for i in 1..3 loop select count(*) into p from positions e_test where mrp=1; end loop; end;', instance=>1); end; / PL/SQL procedure successfully completed. SQL> declare j number; begin dbms_job.submit(job=>j, what=>'declare p number; begin for i in 1..2 loop select count(*) into p from positions e_test where mrp=1; end loop; end;', instance=>2); end; /

  43. Олег Коротков korotkov@devexperts.com Active Session History Example 2. sql_exec_id (Oracle 11g) (2/2). SQL> select sql_id, sql_text from v$sql where sql_id='2dxypmkd8p3qk'; ------------- 2dxypmkd8p3qk SELECT COUNT(*) FROM POSITIONS E_TEST WHERE MRP=1 SQL> select inst_id, sql_exec_id, to_char(sql_exec_id,'XXXXXXXX') sql_exec_id_h, count(*) s from gv$active_session_history where sql_id='2dxypmkd8p3qk' group by inst_id, sql_exec_id order by 1,2; INST_ID SQL_EXEC_ID SQL_EXEC_ S ---------- ----------- --------- ---------- 1 16777216 1000000 4 1 16777217 1000001 4 1 16777218 1000002 5 2 33554432 2000000 5 2 33554433 2000001 4

  44. Олег Коротков korotkov@devexperts.com Active Session History ASH is great tool for: - Investigate load spikes within an AWR snapshot. - Analyze ‘long’ queries executions (especially in 11g). - Investigate locking/blocking issues (if locking time not too short). Limitations: - The information is not complete. ASH on disk is more incomplete. - DB activity spikes makes ‘retention window’ of ASH in memory shorter (sometimes dramatically). - Tends to sample ‘long’ events. - Licensing as part of AWR.

  45. Олег Коротков korotkov@devexperts.com References Oracle® Database Documentation, 11g Release 2 (11.2) Oracle® Database Performance Tuning Guide 5 Automatic Performance Statistics http://docs.oracle.com/cd/E11882_01/server.112/e16638/autostat.htm Oracle® Database PL/SQL Packages and Types Reference 161 DBMS_WORKLOAD_REPOSITORY http://docs.oracle.com/cd/E11882_01/appdev.112/e25788/d_workload_repos.htm Mike Ault. AWR Report Detailed Analysis. http://www.nyoug.org/Presentations/2008/Sep/Ault_AWR.pdf John Beresniewicz. Practical Active Session History TanelPoder. What the heck is the SQL Execution ID – SQL_EXEC_ID? http://blog.tanelpoder.com/2011/10/24/what-the-heck-is-the-sql-execution-id-sql_exec_id/

  46. Олег Коротков korotkov@devexperts.com Thank you for coming! Questions?

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