Hi,
Just answer your question:
Whenever an SAP user starts a transaction (an ABAP program), the work process processing the request always requires the user context.
work process does the real work of the user request.
>I want to know from where the user context is copied from ?
=>Memory(SAP Roll area, SAP extended memory, and heap memory.)
>when the user context is processed mean before request going to dispatcher or after assigning request to work processes?
=> After assigning request to work processes
Regarding of User Context, please refer to
https://help.sap.com/saphelp_nw73ehp1/helpdata/en/49/328da7e8955719e10000000a42189b/content.htm
Best Regards,
Shi Feng