Hello Ratana,
if you are looking for a standard documentation, then you can check this official SAP paper (little bit outdated, but most is still valid):
http://help.sap.com/printdocu/core/print46c/en/data/pdf/MYSAP/SR_PM.pdf
In addition you can also browse the SAP webpages - here you will all necessary basic information.
Regards,
P