This document summarizes Oracle Closed World 2010 and discusses using the Average Active Sessions (AAS) metric to analyze database performance. It shows how to extract AAS data from the AWR tables and graph it over time to identify performance bottlenecks. Linear regression is applied to the AAS and CPU utilization data to quantify their relationship and help determine capacity planning needs. The document provides references and tools for further performance analysis and consolidation best practices.

1. Oracle Closed World 2010:
Graphing the AAS ala EM + doing
some cool linear regression

2. Who am I?
• Karl Arao, Oracle ACE, OCP‐DBA, RHCT
• Solutions Architect / Principal Consultant @ SQL*Wizard
• Blog: http://karlarao.wordpress.com
• Wiki: http://karlarao.tiddlyspot.com

3. DBA_HIST_* tables

4. My first close encounter

5. gc block lost
http://karlarao.wordpress.com/2009/06/07/diagnosing-and-resolving-gc-block-lost

6. AWR Scripts

7. Visualization

8. Can’t go back in time?

9. AAS – Average Active Sessions
Kyle Hailey: http://www.perfvision.com/ftp/emea_2010_may/02_AAS.ppt
Max CPU
Max CPU

10. AAS – the Golden Metric
AAS & CPU count as a yardstick for a possible performance problem (I suggest reading Kyle's
stuff about this):
if AAS < 1
‐‐ Database is not blocked
AAS ~= 0
‐‐ Database basically idle
‐‐ Problems are in the APP not DB
AAS < # of CPUs
‐‐ CPU available
‐‐ Database is probably not blocked
‐‐ Are any single sessions 100% active?
AAS > # of CPUs
‐‐ Could have performance problems
AAS >> # of CPUS
‐‐ There is a bottleneck

11. awr_topevents.sql

12. Textual trends

16. AAS throughout the AWR retention
period!
http://karlarao.wordpress.com/2010/07/25/graphing-the-aas-with-perfsheet-a-la-enterprise-manager

17. Capacity Planning

18. awr_genwl.sql

19. http://karlarao.wordpress.com/2010/01/31/workload-characterization-using-dba_hist-tables-and-ksar

20. U = R / C

21. where aas > 1

22. Filter the data points
• AAS range
aas > 1
• Per SNAP_ID or range of SNAP_IDs
id in (336)
where id >= 336 and id <= 340
• Oracle CPU Utilization
oracpupct > 50
• OS CPU Utilization
oscpupct > 50
• Workload periods
AND TO_CHAR(s0.END_INTERVAL_TIME,'D') >= 1 ‐‐ Day of week: 1=Sunday 7=Saturday
AND TO_CHAR(s0.END_INTERVAL_TIME,'D') <= 7
AND TO_CHAR(s0.END_INTERVAL_TIME,'HH24MI') >= 0900 ‐‐ Hour
AND TO_CHAR(s0.END_INTERVAL_TIME,'HH24MI') <= 1800
AND s0.END_INTERVAL_TIME >= TO_DATE('2010‐jan‐17 00:00:00','yyyy‐mon‐dd hh24:mi:ss') ‐‐ Data range
AND s0.END_INTERVAL_TIME <= TO_DATE('2010‐aug‐22 23:59:59','yyyy‐mon‐dd hh24:mi:ss‘)

24. Straight line graph: Slope‐Intercept Form
y = mx + b

25. AAS vs. CPU% utilization
http://karlarao.tiddlyspot.com/#r2project

33. “oracpupct” column also has a good linear fit. Since the
server’s load is CPU centric (see top r2 stats from .92 and
above), why not use it?
AAS(y) against CPU% Utilization(x) will be more
meaningful/readable instead of “CPU used by this session”

34. AAS vs. CPU% utilization
http://karlarao.tiddlyspot.com/#r2project

35. Drilling down on the peak workload...
with AAS of 10

36. AAS vs. CPU% utilization
http://karlarao.tiddlyspot.com/#r2project

41. Now on the low workload period...
with AAS of 2.2

42. AAS vs. CPU% utilization
http://karlarao.tiddlyspot.com/#r2project

46. Conclusion

47. References and Tools
• http://karlarao.wordpress.com
– http://karlarao.tiddlyspot.com/#%5B%5BStorage%20IOPS%2Ccapacity%2Cperformance
%2Ccost%5D%5D
– http://karlarao.tiddlyspot.com/#Statistics
– http://karlarao.tiddlyspot.com/#OraclePerformance
• Tanel Poder @ http://blog.tanelpoder.com
– http://www.tanelpoder.com/files/TPT_public.zip
– http://www.tanelpoder.com/files/PerfSheet.zip
– Neil Gunther & Tanel Poder ‐ Multidimensional Visualization of Oracle Performance
using Barry007 http://arxiv.org/pdf/0809.2532
• Kyle Hailey @ http://ashmasters.com , http://www.perfvision.com
• Craig Shallahamer @ orapub.com
– Introduction To Oracle Server Consolidation
http://resources.orapub.com/product_p/server_consolidation_ppt.htm
• Husnu Sensoy @ husnusensoy.wordpress.com
– Database Consolidation Best Practices
http://husnusensoy.files.wordpress.com/2010/05/database‐consolidation‐best‐
practices.pdf
• Andy Rivenes @ http://www.appsdba.com/pubs.htm
• Neeraj Bhatia @ www.nioug.org/files/Linear_Regression.pdf

48. Contact me through:
karao@sqlwizard.com