Performance considerations when upgrading Solaris
By user9166071 on Jan 19, 2009
"We recommend that you start with an empty /etc/system file when moving to a new Solaris
release. As a first step, add only those tunables that are required by in-house or third-party
applications. Any tunables that involve System V IPC (semaphores, shared memory, and
message queues) have been modified in the Solaris 10 release and should be changed in your
environment. For more information, see “System V IPC Configuration” on page 21. After
baseline testing has been established, evaluate system performance to determine if additional
tunable settings are required."
So, that's a move it out of the way and start from scratch. :) Obviously speak to your application vendors about anything that is required to run the application but other than that, see how things go and only change when and where necessary otherwise you could run into other problems.
The only application which I'll make specific points about is Oracle as with Solaris 10 we've introduced resource controls so the shared memory / semaphore settings no longer need to be defined in /etc/system. See the Oracle installation guide or Solution 208623 : Solaris[TM] 10 Operating System: System V Inter-Process Communication (IPC) resource controls for further details.