1. ASH – Active Session History Feel the Power
Kyle Hailey

2. Why should you care? Because ASH can Change your life …
10g immediately Accessible
Geeks: Via scripts in SQL
Managers : Graphical OEM
Stuck on Oracle 7,8,9 ?
… my apologies because 10g rocks, but …
no worries, the data is accessible for you too via scripts
Copyright 2006 Kyle Hailey

3. Revolution and an Evolution
Oracle 6 … ie the dark ages … there was once the Cache Buffer Hit Ratio
Oracle 7 … turned the lights on … Wait Events … hallelujah I can see the light
Oracle 10g … ASH has landed
(like the wheels on the suitcases)
Copyright 2006 Kyle Hailey

4. Sampling New Paradigm Clear Vision of the future Cheaper
Use new sampling technology
Lets go of the need to know 100%
Statistical approximation
Cheaper
Richer Multidimensional Data
Identifies
SQL
Sessions
Objects
Machine
User
Sampling is a leap in performance tuning technology. It took a clear vision of the future and a bit of a leap of faith to let go of the compulsive need to have exact measurements and instead embrace sampling a technology that statistically approximates the same value with little loss of accuracy but at the same time brings a much great wealth of information necessary for analyzing the performance of a database.
Copyright 2006 Kyle Hailey

5. Identify Players before ASH
Sessions v$sesstat, v$session_event
# sessions x (# wait events + statistics)
Example (150 x ( ) = 150,000 )
SQL
v$sql
Could be 10000s
Takes out latches that compete with other sql executions
Objects
V$segstat 9i+
Could be 1000s of objects
Also files v$filestat
Expensive !
Copyright 2006 Kyle Hailey

6. ASH Intelligence for the new Millennium
Intelligently Collects Data
Samples once a second
Collects active sessions only
Collects Session/SQL/Wait
More activity, more data collected
Less activity, less data collected
Those old methods collected everything
Obfuscated the problem, too many statistics too late
Costly
Too Granular – once an hour ?! Give me a break
Collects fine grain multidimensional data
Copyright 2006 Kyle Hailey

7. ASH Fields SAMPLE_TIME TIMESTAMP(3) SESSION_ID NUMBER
SQL> v$active_session_history
Name Null? Type
SAMPLE_ID NUMBER
SAMPLE_TIME TIMESTAMP(3)
SESSION_ID NUMBER
SESSION_SERIAL# NUMBER
USER_ID NUMBER
SQL_ID VARCHAR2(13)
SQL_CHILD_NUMBER NUMBER
SQL_PLAN_HASH_VALUE NUMBER
SQL_OPCODE NUMBER
SERVICE_HASH NUMBER
SESSION_TYPE VARCHAR2(10)
SESSION_STATE VARCHAR2(7)
QC_SESSION_ID NUMBER
QC_INSTANCE_ID NUMBER
EVENT VARCHAR2(64)
EVENT_ID NUMBER
EVENT# NUMBER
SEQ# NUMBER
P NUMBER
P NUMBER
P NUMBER
WAIT_TIME NUMBER
TIME_WAITED NUMBER
CURRENT_OBJ# NUMBER
CURRENT_FILE# NUMBER
CURRENT_BLOCK# NUMBER
PROGRAM VARCHAR2(48)
MODULE VARCHAR2(48)
ACTION VARCHAR2(32)
CLIENT_ID VARCHAR2(64
Copyright 2006 Kyle Hailey

8. v$active_session_history
SAMPLE_ID NUMBER
SAMPLE_TIME TIMESTAMP(3)
When
SESSION_ID NUMBER
SESSION_SERIAL# NUMBER
USER_ID NUMBER
SERVICE_HASH NUMBER
SESSION_TYPE VARCHAR2(10)
PROGRAM VARCHAR2(64)
MODULE VARCHAR2(48)
ACTION VARCHAR2(32)
CLIENT_ID VARCHAR2(64)
Session
State
SESSION_STATE VARCHAR2(7)
WAIT_TIME NUMBER
EVENT VARCHAR2(64)
EVENT_ID NUMBER
EVENT# NUMBER
SEQ# NUMBER
P NUMBER
P NUMBER
P NUMBER
WAIT_TIME NUMBER
TIME_WAITED NUMBER
CURRENT_OBJ# NUMBER
CURRENT_FILE# NUMBER
CURRENT_BLOCK# NUMBER0
Wait
WAIT_TIME is time of last wait, > 0 , means on CPU
TIME_WAITED is the actual wait time
SQL
SQL_ID VARCHAR2(13)
SQL_CHILD_NUMBER NUMBER
SQL_PLAN_HASH_VALUE NUMBER
SQL_OPCODE NUMBER
QC_SESSION_ID NUMBER
QC_INSTANCE_ID NUMBER
Duration
TIME_WAITED NUMBER
Copyright 2006 Kyle Hailey

9. Primary Fields of ASH SAMPLE_TIME Time SESSION_ID Session
Activity : Who, What, When, How
When
SAMPLE_TIME
Time
SESSION_ID
Who
Session
SESSION_STATE
State
How
EVENT
Wait
What
SQL_ID
SQL
Copyright 2006 Kyle Hailey

10. Amazing things YOU can do
Top SQL
SQL ID
Plan
Child#
Top Consumers
Session
User
Object
Module.Action
Program
Service
Client
Wait
Top Resources
CPU
Waits
Event (800*)
I/O
File
Block
Time X X
And Aggregated over any time Period
(32 columns in ASH 10.1)
Copyright 2006 Kyle Hailey

11. Multi-dimensional SQL Statistics Waits Sessions 06/05/08 Program User
F1qcyh20550cf
fj6gjgsshtxyx
0cjsxw5ndqdbc
8t8as9usk11qw
dr1rkrznhh95b
10dkqv3kr8xa5
38zhkf4jdyff4
298wmz1kxjs1m
Package
Procedure
Plan
Child #
Statistics
Waits
CPU
Enq: TX – row lock contention
SQL*Net break/reset to client
db file scattered read
db file sequential read
Sessions
Program
Sqlplus
Toad
User
Sys
Scott
System
Application
Service GL OE IO
06/05/08

12. Groupings – Top Consumer
SESSION_ID
SESSION_SERIAL# (identify SID reuse)
SESSION_TYPE (FOREGROUND,BACKGROUND)
USER_ID (SYS, SYSTEM, SCOTT etc)
SERVICE_HASH (OE,GL,HR)
MODULE.ACTION (PLSQL tagging)
CLIENT_ID (identifying users in session pool)
PROGRAM (SQL, JDBC, Forms etc)
SQL_ID
QC_SESSION_ID (Query Coordinator)
QC_INSTANCE_ID (RAC)
EVENT + P1, P2, P3
CURRENT_OBJ#
CURRENT_FILE#
CURRENT_BLOCK#
Copyright 2006 Kyle Hailey

13. Top CPU Session Top CPU consuming Session in last 5 minutes Select
session_id,
count(*)
from
v$active_session_history
where
session_state= ‘ON CPU‘ and
SAMPLE_TIME > sysdate – (5/(24*60))
group by
session_id
order by
count(*) desc;
Who is the rogue session ?
Copyright 2006 Kyle Hailey

14. Results Top CPU Session
SESSION_ID COUNT(*)
Select
session_id, session_serial# ,
count(*) ,
round((count(*)*100)/(5*60),0) "%",
lpad('*',round((count(*)*10)/(5*60),0),'*') "Bar"
from
v$active_session_history
where
session_state= 'ON CPU' and
SAMPLE_TIME > sysdate - (5/(24*60))
group by
session_id, session_serial#
order by
count(*) desc /
Copyright 2006 Kyle Hailey

15. CPU with Bars Bar shows 10% increments SESSION_ID COUNT(*) % Bar
|**********|
|** |
|* |
| |
| |
| |
| |
Graphics – humans can process 400,000 times as much data graphically as textually
Think of a map of the US and all the counties with birth rates colored from low to high.
It’s a massive about of information textually but it can all be seen on one page of a map
Select
session_id, session_serial# ,
count(*) ,
round((count(*)*100)/(5*60),0) "%",
lpad('*',round((count(*)*10)/(5*60),0),'*') "Bar"
from
v$active_session_history
where
session_state= 'ON CPU' and
SAMPLE_TIME > sysdate - (5/(24*60))
group by
session_id, session_serial#
order by
count(*) desc /
Bar shows 10% increments
Copyright 2006 Kyle Hailey

16. Top Waiting Session Top Waiting Session in last 5 minutes Select
session_id,
count(*)
from
v$active_session_history
where
session_state=‘WAITING’ and
SAMPLE_TIME > SYSDATE - (5/(24*60))
group by
session_id
order by
count(*) desc;
Copyright 2006 Kyle Hailey

17. Top Waiting Session Results
SESSION_ID COUNT(*)
Copyright 2006 Kyle Hailey

18. Top SQL from ASH select ash.SQL_ID ,
sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
sum(decode(ash.session_state,'WAITING',1,0)) -
sum(decode(ash.session_state,'WAITING', decode(en.wait_class, 'User I/O',1,0),0)) "WAIT" ,
sum(decode(ash.session_state,'WAITING', decode(en.wait_class, 'User I/O',1,0),0)) "IO" ,
sum(decode(ash.session_state,'ON CPU',1,1)) "TOTAL"
from v$active_session_history ash,
v$event_name en
where SQL_ID is not NULL and en.event#=ash.event#
group by sql_id
order by sum(decode(session_state,'ON CPU',1,1)) desc
select
ash.SQL_ID ,
sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
sum(decode(ash.session_state,'WAITING',1,0)) -
sum(decode(ash.session_state,'WAITING', decode(en.wait_class, 'User I/O',1,0),0)) "WAIT" ,
sum(decode(ash.session_state,'WAITING', decode(en.wait_class, 'User I/O',1,0),0)) "IO" ,
sum(decode(ash.session_state,'ON CPU',1,1)) "TOTAL"
from v$active_session_history ash,
v$event_name en
where SQL_ID is not NULL and en.event#=ash.event#
group by sql_id
order by sum(decode(session_state,'ON CPU',1,1)) desc
Copyright 2006 Kyle Hailey

19. Top SQL from ASH Results
SQL_ID CPU WAITING IO TOTAL
4c1xvq9ufwcjc
6wjw6rz5uvbp
968dm8hr9qd
938jp5gasmrah
cv8xnv81kf
6p9bzu19v965k
5zu8pxnun66bu
db2jr13nup72v
7ks5gnj38hghv
Copyright 2006 Kyle Hailey

20. Top Session select ash.session_id, ash.session_serial#, ash.user_id,
ash.program,
sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
sum(decode(ash.session_state,'WAITING',1,0)) -
sum(decode(ash.session_state,'WAITING',
decode(en.wait_class,'User I/O',1, 0 ), 0)) "WAITING" ,
decode(en.wait_class,'User I/O',1, 0 ), 0)) "IO" ,
sum(decode(session_state,'ON CPU',1,1)) "TOTAL"
from v$active_session_history ash,
v$event_name en
where en.event# = ash.event#
group by session_id,user_id,session_serial#,program
order by sum(decode(session_state,'ON CPU',1,1))
select
ash.session_id,
ash.session_serial#,
ash.user_id,
ash.program,
sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
sum(decode(ash.session_state,'WAITING',1,0)) -
sum(decode(ash.session_state,'WAITING',
decode(en.wait_class,'User I/O',1, 0 ), 0)) "WAITING" ,
decode(en.wait_class,'User I/O',1, 0 ), 0)) "IO" ,
sum(decode(session_state,'ON CPU',1,1)) "TOTAL"
from v$active_session_history ash,
v$event_name en
where en.event# = ash.event#
group by session_id,user_id,session_serial#,program
order by sum(decode(session_state,'ON CPU',1,1))
Copyright 2006 Kyle Hailey

21. Top Session Results SESSION_ID SERIAL# USER_ID PROGRAM CPU WAITING IO
sqlplus
(LGWR)
(CKPT)
(DBW0)
(PMON)
Executor.exe
Executor.exe
Executor.exe
Executor.exe
Copyright 2006 Kyle Hailey

22. Top Session w/ Username
select
decode(nvl(to_char(s.sid),-1),-1,'DISCONNECTED','CONNECTED')
"STATUS",
topsession.session_id "SESSION_ID",
u.name "NAME",
topsession.program "PROGRAM",
max(topsession.CPU) "CPU",
max(topsession.WAITING) "WAITING",
max(topsession.IO) "IO",
max(topsession.TOTAL) "TOTAL"
from ( {previous query} ) topsession,
v$session s,
user$ u
where
u.user# =topsession.user_id and
/* outer join to v$session because the session might be disconnected */
topsession.session_id = s.sid (+) and
topsession.session_serial# = s.serial# (+)
group by topsession.session_id, topsession.session_serial#, topsession.user_id,
topsession.program, s.username,s.sid,s.paddr,u.name
order by max(topsession.TOTAL) desc
Copyright 2006 Kyle Hailey

23. Top Session Finding a Rogue User
STATUS SESSION_ID NAME PROGRAM CPU WAITING IO
CONNECTED CPU_Monger ChMgr304.exe
CONNECTED SYS (LGWR)
CONNECTED SYS (DBW0)
CONNECTED SYS (CKPT)
CONNECTED SYS (PMON)
DISCONNECTED SYSTEM Executor.exe
DISCONNECTED SYSTEM Executor.exe
DISCONNECTED SYSTEM Executor.exe
Copyright 2006 Kyle Hailey

24. Many Ways to Attack Problems
Confusing
How to Attack the problem?
Top SQL?
Top wait for that SQL?
Top Waiting Session ?
Top Waits for that Session
Top Waits for Database?
Top Session waiting for that wait
Top SQL for that wait
Solution - Graphics
Copyright 2006 Kyle Hailey

25. Mining Data is Non Trivial
Many Dimensions to consider
Constantly Varying time frames
Luckily 10g automates all of this functionality.
collects all of the data
analyses all the wait events
reports on bottlenecks
supplies solutions
Graphics add tremendous ease and power
Copyright 2006 Kyle Hailey

26. OEM Perf Page
Copyright 2006 Kyle Hailey

27. ASH Sampling Cheap Cost Size
With PL/SQL it’s less that 1 % CPU with 10 average active sessions
DMA - direct memory attach to SGA Using C code 200x Cheaper
ASH in 10g should be even cheaper than DMA because it’s done in the kernel
Size
Circular Buffer - 1M to 128M (~2% of SGA)
Avg row around 150bytes
3600 secs in an hour
~ ½ Meg per Active Session per hour
Copyright 2006 Kyle Hailey

28. How ASH works V$session_wait+ v$session + extras MMON/MMNL
v$active_session_history
Only writes out 1 in 10 rows via direct path inserts
wrh$_active_session_history
MMON - manageability monitor, AWR
M000 – MMON background slave, runs snapshots
MMNL - MMON lite, flushes ASH to disk
Copyright 2006 Kyle Hailey

29. ASH buffer Select reads backwards No latching Index on time
No read consistency
Insert point
Insert one direction
Touch up wait times
Copyright 2006 Kyle Hailey

30. Family of ASH Tables Real time v$session ~2 hours
(before 10g v$session_wait)
Last 10 waits
v$session_wait_history
~2 hours
v$active_session_history
1 week
DBA_HIST_ACTIVE_SESS_HISTORY
wrh$active_session_history
Copyright 2006 Kyle Hailey

31. Oradebug Dump to trace file SQL> oradebug dump ashdump 5
SQL> Alter session set events ‘immediate
tracename ashdump level 5’;
level 5 = # of minutes
loader file rdbms/demo/ashldr.ctl
SQL> oradebug dump ashdump 5
SQL> Alter session set events ‘immediate
trace name ashdump level 5’;
Copyright 2006 Kyle Hailey

32. INIT.ORA statistics_level = Typical (default)
PARAMETER SESSION_VALUE INSTANCE_VAL
_ash_sampling_interval
milliseconds
_ash_size
ASH buffer size
_ash_enable TRUE TRUE
Turn on/off ASH sampling, flushing and the V$ views on ASH
_ash_disk_write_enable TRUE TRUE
Flush to disk
_ash_disk_filter_ratio
write 1 in 10 points
_ash_sample_all FALSE FALSE
Sample including idle waits
ASH
_ash_enable = false; [ A dynamic parameter will turn off ASH sampling, flushing and the V$ views on ASH ]
ADDM
_addm_auto_enable = false; [ A dynamic parameter to turn off automatic ADDM runs after every AWR snapshot ]
AWR
"_swrf_mmon_flush" = FALSE ; AWR
metrics
"_swrf_mmon_metrics" = FALSE ; METRICS
DB Feature Usage
"_swrf_mmon_dbfus" = FALSE ; DB Feature Usage
"_swrf_on_disk_enabled" = FALSE ; disable all (on disk, including manual) AWR operations:
Copyright 2006 Kyle Hailey

33. 10.2 ASH Extras Blocking Session ! Parameter Names Wait Grouping XID
BLOCKING_SESSION_STATUS
BLOCKING_SESSION_SERIAL#
RAC event Fixup
Plan Hash Fix up
10gR1 - during parsing no plan, good way to find parsing problems
10gR2 – get plan hash fixup – good but lose some ability to find parsing problems
Parameter Names
P1TEXT , P2TEXT, P3TEXT
Wait Grouping
WAIT_CLASS
WAIT_CLASS_ID
XID
FORCE_MATCHING_SIGNATURE
Cursor sharing
6/2/2018 33 33

34. ASH Extras
PLSQL_ENTRY_OBJECT_ID PLSQL_ENTRY_SUBPROGRAM_ID PLSQL_OBJECT_ID PLSQL_SUBPROGRAM_ID
ALL_PROCEDURES
where object_id = plsql_object_id
and subprogram_id = plsql_subprogram_id
6/2/2018 34 34

35. PLSQL Tracking Package/Procedure/SQL tracking 10.2.0.3
calling_code SQL_ID COUNT(*)
ORDERENTRY.NEWORDER uuqgjq7k12nf
ORDERENTRY.NEWCUSTOMER bzhqhhj9mpaa
ORDERENTRY.BROWSEANDUPDATEORDERS 41zu158rqf4kf
ORDERENTRY.NEWORDER yas01u2p9ch
PARSE_SAME vjxpmhhzngu
ORDERENTRY.BROWSEANDUPDATEORDERS 05s4vdwsf
set linesize 120
col entry_package for a25
col entry_procedure for a25
col cur_package for a25
col cur_procedure for a25
col calling_code for a70
select
procs1.object_name || decode(procs1.procedure_name,'','','.')||
procs1.procedure_name ||' '||
decode(procs2.object_name,procs1.object_name,'',procs2.object_name) ||
decode(procs2.procedure_name,procs1.procedure_name,'',
decode(procs2.procedure_name,'','',null,'','.')||procs2.procedure_name)
"calling_code",
sql_id,
count(*)
from v$active_session_history ash,
all_procedures procs1,
all_procedures procs2
where
ash.PLSQL_ENTRY_OBJECT_ID = procs1.object_id (+)
and ash.PLSQL_ENTRY_SUBPROGRAM_ID = procs1.SUBPROGRAM_ID (+)
and ash.PLSQL_OBJECT_ID = procs2.object_id (+)
and ash.PLSQL_SUBPROGRAM_ID = procs2.SUBPROGRAM_ID (+)
and ash.sample_time > sysdate - &minutes/(60*24)
group by procs1.object_name, procs1.procedure_name,
procs2.object_name, procs2.procedure_name,sql_id
order by count(*) /
select
object_name package||.|| procedure_name, sql_id, count(*)
from v$active_session_history ash,
all_procedures procs
where
ash.PLSQL_ENTRY_OBJECT_ID = procs.object_id
and ash.PLSQL_ENTRY_SUBPROGRAM_ID = procs.SUBPROGRAM_ID
6/2/2018 35 35

36. 11.1g ASH extras SQL Elapsed Operation bit vector – non timed ops
 SQL_EXEC_ID
 SQL_EXEC_START
 IN_CONNECTION_MGMT
 IN_PARSE
 IN_HARD_PARSE
 IN_SQL_EXECUTION
 IN_PLSQL_EXECUTION
 IN_PLSQL_RPC
 IN_PLSQL_COMPILATION
 IN_JAVA_EXECUTION
 IN_BIND
 IN_CURSOR_CLOSE
SQL Row Source
SQL_PLAN_LINE_ID
 SQL_PLAN_OPERATION
 SQL_PLAN_OPTIONS
Which instance requested block?
 REMOTE_INSTANCE#
ETC
Recursive SQL
CURRENT_ROW# 
 EVENT# 
 QC_SESSION_SERIAL#
 CONSUMER_GROUP_ID
 FLAGS
TOP_LEVEL_SQL_ID
TOP_LEVEL_SQL_OPCODE
Copyright 2006 Kyle Hailey 36

37. 11.2g ASH extras Statistics TM_DELTA_TIME TM_DELTA_CPU_TIME
TM_DELTA_DB_TIME
DELTA_TIME
DELTA_READ_IO_REQUESTS
DELTA_WRITE_IO_REQUESTS
DELTA_READ_IO_BYTES
DELTA_WRITE_IO_BYTES
DELTA_INTERCONNECT_IO_BYTES
PGA_ALLOCATED
TEMP_SPACE_ALLOCATE
Copyright 2006 Kyle Hailey 37

38. ASH Across Versions When Who SQL
ASH instrumentation is exploding across the versions
Waits
Statistics
Blocker
10.1
10.2
11.1
11.2
Copyright 2006 Kyle Hailey

39. How Many Active Sessions?
How much data does ASH Collect ?
1 CPU means max 1 Avg Active Session unless there is a bottleneck
Big site examples:
Oracle 4 way RAC internal apps
10,000 connected, 200 active
One Site
3000 connected, 30 Active
Site
12,000 connected, 100 active
Copyright 2006 Kyle Hailey

40. ASH Summary Rich & Multidimensional Sampling is the future
Overview of system load
Drilldowns into problems
Sql
Session
Wait event
Details information on problem resolution
Sampling is the future
Took clean vision to create - Bit of a leap of faith
Less Accurate but more powerful than past
Inaccuracies unimportant for the most part
Feasible since version 7
You can implement it yourself
OEM simplifies mining of ASH data
Copyright 2006 Kyle Hailey

41. Q1
How can you immediately find the top IO consuming SQL statement in the last 60 seconds
a. v$active_session_history
b. v$sqlstats
c. v$sql
d. v$sqlarea
answer
a only
others
b,c,d - only have cumulative values since database startup
Copyright 2006 Kyle Hailey

42. Q2
Which view can you query directly to get the specific waits that occurred 30 minutes ago:
a. v$active_session_history
b. v$waitclassmetric
c. v$system_event
d. v$session_wait_history
e. v$waitclassmetric_history
answer
b - last 60 seconds only
others
a only
c - cumulative info since db startup
e - only wait groups, not wait events, but has the history for last hour
d - last 10 waits only
Chapt 1 ASH
8 ====================================================================
analyzing database performance. The view v$active_session_history is new in 10g,
ASH (v$active_session_history) is a revolutionary data source for monitoring and
but most of the data needed in order to simulate v$active_session_history by hand
has been available since which version
b. 7
a. 6
c. 8
e. 10
d. 9
which is the foundation for ASH
b - since version 7 when wait events were introduced along with the view v$session_wait
4 ====================================================================
How can immediate find the top IO consuming SQL statement in the last 60 seconds
c. v$sql
b. v$sqlstats
a. v$active_session_history
d. v$sqlarea
b,c,d - only have cumulative values since database startup
a only
b - last 60 seconds only
c - cumulative info since db startup
d - last 10 waits only
e - only wait groups, not wait events, but has the history for last hour
Copyright 2006 Kyle Hailey

43. Q3
ASH (v$active_session_history) is a revolutionary data source for monitoring and analyzing database performance. The view v$active_session_history is new in 10g, but most of the data needed in order to simulate v$active_session_history by hand has been available since which version
a. 6
b. 7
c. 8
d. 9
e. 10
b - since version 7 when wait events were introduced along with the view v$session_wait
which is the foundation for ASH
answer
Chapt 1 ASH
4 ====================================================================
How can immediate find the top IO consuming SQL statement in the last 60 seconds
c. v$sql
b. v$sqlstats
a. v$active_session_history
d. v$sqlarea
others
a only
b,c,d - only have cumulative values since database startup
Copyright 2006 Kyle Hailey