Troubleshooting SAP Performance Issues

Is there a document that will help me troubleshoot system performance? What are the steps on how to troubleshoot?

Troubleshooting is a BIG task of itself, there is no single reference document because there are too many reasons why a system can appear "slow" to the user:

- Different Databases

Every database has its own mechanism for optimizing access, even more, each database has BOOKS on performance optimization. This can start from parameters to database layout to operating system configuration, used filesystems, mount parameters...

- Different Operating System

The same goes for operating systems, a standard Windows 2000 (or 2003) isn´t configured for optimal throughput, there is a LOT to tune, e. g. enable "background process priorities", stop non-needed services, network configurations (TCP window sizes) etc. Also the connection between application and database servers can be an issue

- SAP Itself

Almost for each and every long running program there are optimizations, be it on ABAP layer or on selection layer. Out of my experience, most self developed programs (Z*-programs) are the main issue, because developers program "quick-and-dirty"
doing "select *" and other things.

For e.g.:

If CPU is 100% Busy, what action should be taken to keep CPU idle?

This can't be answered generally. One need to check what process is using so much CPU - then one can start digging deeper. To add info regarding this issue, you may use:

st06->details analysis menu->snapshot analysis->top CPU from there, start to narrow down.