We are planning to do a System Capacity analysis for the system which has been running for more than one year.  In operating system, we have had the monitor on CPU, Memory, Disk and Process. Now we want to do some analysis from application or service level. The application we are using is Siebel eConsumer goods, Partner portal and Siebel analytics.

Anybody who has the experiences about this system capacity analysis on application level with Siebel, can you please share with us?

The questions are like below:

What items should be considered to measure the system capacity? (concurrent user? service response time? etc.)
What do you do to improve the system capacity? (system configuration adjustment?)