Vijay Adik vadik@us - IBM

5
IBM Advanced Technical Support - Americas
Performance Overview – Tuning Methodology
Iterative Tuning Process
�Stress System (i.e., Tune at Peak workload)
�Monitor Sub-Systems
�Identify Predominant Bottleneck
�Tune Bottleneck
�Repeat
CPU Memory Network I/O
© 2009 IBM Corporation
Predominant Bottleneck
• Understand the external view of system performance
The external view of system performance is the
observable event that is causing someone to say
the system is performing poorly. Typically, (1)
end-user response time, (2) application (or task)
response time or (3) throughput. Should not use
system metrics to judge improvement.
• Performance only improves when the predominant
bottleneck is fixed
Fixing a secondary bottleneck will not improve
performance and typically results in overloading an
already overloaded predominant bottleneck.
• Monitor Performance after a change – Tuning is an
iterative process
Monitoring is required after making a change for
two reasons (1) Fixing the predominant bottleneck
typically uncovers another bottleneck, and (2) Not
all changes yield a positive results. If possible you
should have a “repeatable” test to so change can
be accurately evaluated.
• End-User Response time is the elapsed time between when a user submits a request and receives a response.
• Application Response time is the elapsed required for one or more jobs to complete. Historically, these jobs have been called batch jobs.
• Throughput is the amount of work that can be accomplished per unit time. This metric is typically expressed in terms of transaction per minute.
April 17, 2009