Purchasing Group and User Assignment

Hi,

I have created an user ID "User1" (assume CP, S also created for it) and assigned

to the Purchasing Group "P01" ( "O" level ).

what is the use of assiging the user ID "user1" to the Purchasing Group "P01" ?

Can I assign the User ID "User1" to the multiple Purchasing Groups ?

SRM Version : 5.0 - Extended classic Scenario

With regards,

Pranav