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
- Active Session History (ASH)
- Basic ideas
- 11.2 enhancements
- Typical use cases
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
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…
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
Oracle has a lot of operational statistics/metrics
gathered since the instance startup.
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
SQL> select inst_id, name, value from gv$sysstat
where name in ('physical reads','session logical reads','user
commits','user rollbacks')
order by name, inst_id;
INST_ID NAME
VALUE
---------- ---------------------- ---------1 physical reads
219525005
2 physical reads
905189162
1 session logical reads 5925054313
2 session logical reads 1.7457E+10
1 user commits
5294595
2 user commits
28113236
1 user rollbacks
8455066
2 user rollbacks
150792358
-- All stattistics:
select * from v$statname;
10.2.0.4 = 387; 10.2.0.5 = 395
11.2.0.2 = 628
Олег Коротков
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$system_event
where wait_class='User I/O'
order by twm_total desc, event, inst_id;
INST_ID EVENT
TOTAL_WAITS TIME_WAITED AVERAGE_WAIT TWM_TOTAL
---------- ------------------------- ----------- ----------- ------------ ---------1 db file sequential read
27577537
40274551
1.46 3.8091E+12
2 db file sequential read
159856155
340633564
2.13 3.8091E+12
1 direct path read temp
44837941
8919281
.2 2.9431E+11
2 direct path read temp
122808964
20511343
.17 2.9431E+11
1 direct path read
1435296
1511142
1.05 9.9823E+10
2 direct path read
12075539
8471152
.7 9.9823E+10
-- All events:
select count(*) from v$event_name;
10.2.0.4 = 889; 10.2.0.5 = 916
11.2.0.2 = 1142
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
SQL>
2
3
4
5
6
7
8
select sql_id, execs, rw, LIOs, PhIOs from (
select sql_id, /*sql_text,*/ sum(executions) execs,
sum(rows_processed) rw, sum(buffer_gets) LIOs, sum(disk_reads) PhIOs
from gv$sql
where module='SQL Developer' and rownum>=1
group by sql_id/*, sql_text*/
order by PhIOs desc)
where rownum<=5;
SQL_ID
EXECS
RW
LIOS
PHIOS
------------- ---------- ---------- ---------- ---------3w1fk8r93360m
1
1
8156
348
davt444np8yr7
6
6
3583
289
7b775q3tc69a9
22
22
2899
213
58kz178ugwm87
29
29
2982
96
ayaq4d3bbt7k8
1
3
106
88
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
AWR just makes a copy of system views with
scheduled time interval…
gv$system
_event
gv$sql
…
DB activity
[8AM, 9AM]
Snap at 9 AM
Snap at 8 AM;
done by MMON
gv$sysstat
gv$sysstat
gv$system
_event
gv$sql
…
… and gives a possibility to make a report (diff) based
on two snapshots.
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
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'
)
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
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.
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
Олег Коротков
korotkov@devexperts.com
Automatic Workload Reports
AWR reports 2/8:
Load Profile
~~~~~~~~~~~~
DB Time(s):
DB CPU(s):
Redo size:
Logical reads:
Block changes:
Physical reads:
Physical writes:
User calls:
Parses:
Hard parses:
W/A MB processed:
Logons:
Executes:
Rollbacks:
Transactions:
Per Second
--------------3.1
1.1
167,379.4
70,689.2
769.8
3,480.6
126.5
138.9
46.4
0.1
4.9
0.1
63.2
0.3
8.1
Per Transaction
Per Exec
Per Call
--------------- ---------- ---------0.4
0.05
0.02
0.1
0.02
0.01
20,585.9
8,694.0
94.7
428.1
15.6
17.1
5.7
0.0
0.6
0.0
7.8
0.0
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
AWR report 3/8:
Top 5 Timed Foreground Events
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Avg
wait
% DB
Time(s)
(ms)
time Wait Class
----------- ------ ------ ---------4,667
8
42.3 User I/O
4,085
37.1
1,726
2
15.7 User I/O
208
300
1.9 Applicatio
104
4
.9 Commit
4)
Event
Waits
------------------------------ -----------db file sequential read
618,214
DB CPU
direct path read temp
810,891
enq: TX - row lock contention
693
log file sync
29,137
Host CPU (CPUs:
8 Cores:
8 Sockets:
~~~~~~~~
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
korotkov@devexperts.com
Automatic Workload Reports
AWR reports 4/8:
Wait Event Histogram
<…>
DB/Inst: ######/######
Snaps: 46095-46096
% of Waits
----------------------------------------------Total
Event
Waits <1ms
-------------------------- ----- ----db file sequential read
619.1 22.0
<…>
Waits 64ms
Event
to 2s <32ms
-------------------------- ----- ----db file sequential read
9020 98.5
<…>
Waits 4s
Event
to 2m
<2s
-------------------------- ----- ----db file sequential read
1 100.0
<2ms <4ms <8ms <16ms <32ms <=1s
>1s
----- ----- ----- ----- ----- ----- ----1.8
9.4 37.0 25.0
3.5
1.5
.0
<64ms <1/8s <1/4s <1/2s
<1s
<2s >=2s
----- ----- ----- ----- ----- ----- ----1.0
.3
.1
.1
.0
.0
.0
<4s
<8s <16s <32s < 1m < 2m >=2m
----- ----- ----- ----- ----- ----- ----.0
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
Module: SQL*Plus
SELECT count(*) FROM …
0
N/A
32.8
52.0
47.8 0q694rv7gzkzs
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
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
AWR report 7/8:
IOStat by Function summary
Reads:
Reqs
Function Name
Data
per sec
--------------- ------- ------Direct Reads
45.5G
228.3
Buffer Cache Re
2.4G
171.7
DBWR
0M
0.0
<…>
TOTAL:
48.9G
409.7
DB/Inst: #####/#####
Data
Writes: Reqs
per sec Data
per sec
------- ------- ------12.9145
0M
0.0
.681144
0M
0.0
0M
1.7G
71.4
IOStat by Filetype summary
Reads:
Reqs
Filetype Name
Data
per sec
--------------- ------- ------Temp File
39.6G
224.9
Data File
8.4G
175.2
<…>
TOTAL:
48.9G
409.7
DB/Inst: #####/#####
Data
Writes: Reqs
per sec Data
per sec
------- ------- ------11.2232
0M
0.0
2.37223
1.7G
71.4
13.8572
13.8569
IOStat by Function/Filetype summary
2.8G
2.8G
Snaps: 46095-46096
Data
Waits:
Avg
per sec Count
Tm(ms)
------- ------- ------0M
0
N/A
0M 619.1K
7.1
.493891
0
N/A
89.3 .800808
716.7K
6.3
Snaps: 46095-46096
Data
Small
Large
per sec
Read
Read
------- ------- ------0M
1.6
N/A
.493060
7.1
29.1
89.3 .799977
3.9
31.7
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
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
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.
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
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
select <...>
from dba_hist_snapshot, dba_hist_sys_time_model
<...>
Date
min_snap_id
31.01.2012
121851
30.01.2012
121747
29.01.2012
121643
28.01.2012
121538
27.01.2012
121435
26.01.2012
121329
25.01.2012
121226
max_id DB time
121955 3582,46
121850 3942,73
121746 3225,62
121642 2626,14
121537 -705799,94
121434 3524,76
121328 3935,66
DB CPU
1899,31
1787,58
1587,83
1410,22
-284112,92
1934,44
2004,01
Олег Коротков
korotkov@devexperts.com
Automatic Workload Repository
select <...>
from dba_hist_snapshot, dba_hist_system_event
<...>
Event_name
waits_1
duration_1
gc buffer busy
1378135
1,9
gc cr grant 2-way
5830652
0,2
gc current block 2-way
2783997
0,3
gc cr multi block request 1339350
0,2
gc cr block 2-way
39967
0,3
gc current grant busy
298901
0,7
gc current grant 2-way
1027710
0,2
waits_2
16189
97805
365330
1850738
948740
20273
1164
duration_2
0,4
0,2
0,3
0,2
0,3
0,3
0,3
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.
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.
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.
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’.
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
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).
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
EVENT, P1, P2, P3, TIME_WAITED – wait
information;
event information;
BLOCKING_SESSION, BLOCKING_SESSION_SERIAL#, BLOCKING_INST_ID – locking
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.
information;
Олег Коротков
korotkov@devexperts.com
Agenda
ASH architecture (John Beresniewicz. Practical Active Session
History)
Indexed
on time
V$SESSION
V$SESSION_WAIT
Session
state
objects
V$ACTIVE_SESSION_HISTORY
Readers go
unlatched
Readers go
the
opposite way
MMON Lite Every second
(MMNL)
Writer goes
one
direction
Circular buffer
in SGA
(2MB per CPU)
DBA_HIST_ACTIVE_SESS_HISTORY
Write
1 out of 10
samples
AWR
Every
hour
(or flush)
Directpath
INSERTS
Олег Коротков
korotkov@devexperts.com
Active Session History
ASH in memory – fixed memory consumption, variable time
range.
SQL> select inst_id, bytes/(1024*1024) MB from gv$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$active_session_history group by inst_id;
INST_ID ASH_WINDOW
---------- ------------------------------1 +000000000 07:18:12.038
2 +000000000 07:01:26.268
3 +000000000 10:15:25.558
Samples for every second.
Олег Коротков
korotkov@devexperts.com
Active Session History
ASH on disk – fixed time range controlled by AWR retention.
SQL> select instance_number, (max(sample_time)-min(sample_time)) ASH_window
from dba_hist_active_sess_history group by instance_number;
INSTANCE_NUMBER ASH_WINDOW
--------------- ---------------------------------1 +000000032 04:59:50.479
2 +000000032 04:59:45.743
3 +000000032 04:59:40.818
SQL> select 'ASH in memory' what, count(distinct sample_id) samples_per_hour
2 from v$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’.
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.
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) =
= 155 concurrently executed queries.
Олег Коротков
korotkov@devexperts.com
Active Session History
Example 1.
SQL>
2
3
4
5
6
7
ASH content (1/3):
select to_char(trunc(sample_time,'mi'),'hh24:mi') dd, count(*) c,
count(distinct h.session_id||':'||h.session_serial#) s
from dba_hist_active_sess_history h
where h.instance_number=1 and h.snap_id between 118265 and 118265
and h.sample_time>=to_date('27.12.2011 13:30','dd.mm.yyyy hh24:mi')
and h.sample_time <to_date('27.12.2011 13:45','dd.mm.yyyy hh24:mi')
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
<…>
Олег Коротков
korotkov@devexperts.com
Active Session History
Example 1.
SQL>
2
3
4
5
6
7
…
ASH content (2/3):
select sample_time, count(*) c,
sum(case when sql_id='9g7dr4k9qj1r1' then 1 else 0 end) s
from dba_hist_active_sess_history h
where h.instance_number=1 and h.snap_id between 118265 and 118265
and h.sample_time>=to_date('27.12.2011 13:30','dd.mm.yyyy hh24:mi')
and h.sample_time <to_date('27.12.2011 13:45','dd.mm.yyyy hh24:mi')
group by sample_time order by sample_time;
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
<…>
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 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
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
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.
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
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/
Олег Коротков
korotkov@devexperts.com
Thank you for coming!
Questions?