The 490 is a flat memory box and the Solaris port is smart enough to behave correctly. On the other hand, I have a lab server( Sun v490) running 10.2.0.2 on Solaris9. The shmmax is set to 20GB. My SGA is 12GB and I am seeing only one segment from ipcs. I have not tinkered with the NUMA optimization parameter. Per Metalink note 39926.1, multiple shared memory segments in 10gR2 are there for performance reason. Why is the behaviors of shared memory segments in 10gR2 is different on the same platform (v490 versus 6900)?