Олег Коротков [email protected]

AWR, ASH - use cases and 11.2 enhancements

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

Олег Коротков [email protected]

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

Олег Коротков [email protected]

Олег Коротков [email protected]

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…

Олег Коротков [email protected]

Automatic Workload Repository

Oracle has a lot of operational statistics/metrics gathered since the instance startup.

Олег Коротков [email protected]

Automatic Workload Repository

SQL> select inst_id, name, value from

gv$sysstat

where name in ('physical reads','session logical reads','user commits','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

Олег Коротков [email protected]

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_total desc, 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

Олег Коротков [email protected]

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 PhIOs desc) 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

Олег Коротков [email protected]

Automatic Workload Repository

AWR just makes a copy of system views with scheduled time interval…

gv$sysstat gv$system _event gv$sql DB activity [8AM, 9AM] gv$sysstat gv$system _event gv$sql … …

… and gives a possibility to make a report (diff) based on two snapshots.

Олег Коротков [email protected]

Automatic Workload Repository

AWR configuration.

-

Oracle Diagnostic Pack is required

additional option).

(Oracle EE - STATISTICS_LEVEL = TYPICAL or ALL - (11g) CONTROL_MANAGEMENT_PACK_ACCESS = DIAGNOSTIC or DIAGNOSTIC+TUNING

Олег Коротков [email protected]

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'

)

Олег Коротков [email protected]

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

Олег Коротков [email protected]

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.

Олег Коротков [email protected]

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

Олег Коротков [email protected]

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

---------- ----------

Олег Коротков [email protected]

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

Олег Коротков [email protected]

Automatic Workload Reports

AWR reports 4/8:

Wait Event Histogram DB/Inst: ######/###### Snaps: 46095-46096

<…> <…> <…> db file sequential read 1 100.0 .0 % 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 -------------------------- ----- ----- ----- ----- ----- ----- ----- ----- -----

Олег Коротков [email protected]

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

Module: JDBC Thin Client MERGE INTO … 3c8sz91kt214t 3,609.9 0 N/A 32.8 52.0 47.8 0q694rv7gzkzs Module: SQL*Plus SELECT count(*) FROM …

Олег Коротков [email protected]

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

Олег Коротков [email protected]

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

Олег Коротков [email protected]

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

Олег Коротков [email protected]

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

Олег Коротков [email protected]

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.

Олег Коротков [email protected]

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

Олег Коротков [email protected]

Automatic Workload Repository

select <...> from dba_hist_snapshot, dba_hist_sys_time_model <...>

Date min_snap_id

31.01.2012

121851 30.01.2012

29.01.2012

121747 121643 28.01.2012

27.01.2012

26.01.2012

25.01.2012

121538 121435 121329 121226

max_id DB time DB CPU

121955 3582,46 1899,31 121850 3942,73 121746 3225,62 1787,58 1587,83 121642 2626,14 121537 -705799,94 121434 3524,76 121328 3935,66 1410,22 -284112,92 1934,44 2004,01

Олег Коротков [email protected]

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 gc cr grant 2-way 5830652 0,2 97805 0,2 gc current block 2-way 2783997 0,3 365330 gc cr multi block request 1339350 0,2 1850738 0,3 0,2 gc cr block 2-way 39967 0,3 948740 gc current grant busy 298901 0,7 20273 gc current grant 2-way 1027710 0,2 1164 0,3 0,3 0,3

Олег Коротков [email protected]

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

.

Олег Коротков [email protected]

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.

Олег Коротков [email protected]

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.

Олег Коротков [email protected]

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’.

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

Олег Коротков [email protected]

Олег Коротков [email protected]

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

It is

not aggregated

but..

(like other AWR data).

Олег Коротков [email protected]

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 .

Олег Коротков [email protected]

Agenda

ASH architecture

(John Beresniewicz. Practical Active Session History)

Indexed on time V$SESSION V$SESSION_WAIT V$ACTIVE_SESSION_HISTORY DBA_HIST_ACTIVE_SESS_HISTORY

Session state objects

MMON Lite (MMNL) Readers go the opposite way Readers go unlatched Every second Circular buffer in SGA (2MB per CPU) Writer goes one direction Write 1 out of 10 samples Every hour (or flush) AWR Direct path INSERTS

Олег Коротков [email protected]

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.

Олег Коротков [email protected]

Active Session History

ASH on disk

SQL> select instance_number, (max(sample_time)-min(sample_time)) ASH_window from – fixed time range controlled by AWR retention.

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

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

; WHAT SAMPLES_PER_HOUR ------------- --------------- ASH in memory 3592 ASH on disk 359 1/10 of samples from ‘ASH in memory’.

Олег Коротков [email protected]

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

.

Олег Коротков [email protected]

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 (1

5 minutes

) = = 155 concurrently executed queries .

Active Session History

Example 1. 3 from 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

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 Олег Коротков [email protected]

Олег Коротков [email protected]

…

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

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 <…> Олег Коротков [email protected]

Олег Коротков [email protected]

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 Tanel Poder 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; /

Олег Коротков [email protected]

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

2 33554433

2000001

5 4

Олег Коротков [email protected]

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.

Олег Коротков [email protected]

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 Tanel Poder. 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/

Thank you for coming!

Questions?

Олег Коротков [email protected]