Oracle Database Discussions

I am working with our Linux admin to understand this issue:

We have a Dell server with 4Gb of memory, 1-CPU, OS is RedHat Linux 3.x, for our DEV instance. We are starting to play around with the SGA_TARGET and SGA_MAX_SIZE init.ora parms in our 10g instance.

From other websites, we have read that the LINUX kernel parameter SHMMAX should be set at 2Gb, and that we cannot create an SGA greater than 1.7 Gb (we actually read that if multiple instances are installed, their collective SGA size couldn't exceed 1.7Gb either).

Being new to Oracle, I'm not sure if 1.7Gb is a very generous helping of memory anyway, but we are trying to understand this whole issue. Any advice on the interaction between SGA size and shmmax, and the amount of memory others have provided for their total SGA would be greatly appreciated.

Thanks,
Chuck