Oracle Database Discussions

Ok, I'm an old database developer, but very new DBA.

I am running oracle 10gr2 on AIX 5.3 (I am also completley new to AIX).

The oracle enterprise manger is telling me that my SGA_TARGET is inadequatly sized. It is currently 2864M, and ADDM is suggesting I resize to 4296M.

I have a "test" oracle instance I run on aisanux. It is actually a VM. I tried to do adjust the SGA_TARGET, and found that the SGA_MAX_SIZE kept me from running an alter system set SGA_TARGET = 4000000000 (or there about). So, I changed it in the SP file, restarted, and it won't come up. (insufficent memory). The test box has 2.5 GB allocated and 2GB of swap (I think, not exactly sure how to run the OS).

Anyways, my production box has 8GB physical memory, and as near as I can tell 8GB of paging space. Unfortunatly, it also is running an Application server.

As I understand, the SGA_MAX_SIZE is determined by the SGA_TARGET when 10gR2 starts up. Since I can't change the live SGA_TARGET size because of the SGA_MAX_SIZE, I thought I would change the SGA_MAX_SIZE in the sp file (which is currently blank), restart oracle, and then see if I can change SGA_TARGET. I am concerned if I set the SGA_MAX_SIZE to the 4GB+ that I need, the instance won't come back up due to an insufficient memory error. (I still have not figured out how to restore my test instance; it's got this problem now)

What should I do here?

Thank you