Sga_target ?

I have a 4G memory windows server. I want to create an OLTP database on this machine. I have Oracle 10.2 installed. I want to use 2G of memory for this instance. Can someone please advise whether I should set the SGA_TARGET to 2G and have the server manage the buffer_pool and shared_pool? Can someone please advise whether this is good practice or should I manually set the memory parameters? I never used this parameter before and I am not sure what impact it might have on performance. Thank you.

just use the auotmatic stuff, if it doesnt work for you change it

Thats a pretty small server so it will get it mostly right

Just remember that if you keep the old parameters set, they become the minimum size the respective pool will shrink to. If you have them set too high, you will limit Oracle's ability to make its own mind up about how it should share about the memory.