Question : Sizing SGA after adding extra memory

I have added additional RAM to the sun solaris server hosting oracle8 to improve performence. What is the best way compute the availabe free physical memory on this server and then to evaluate new init.ora parameters for SGA to include this additional RAM?

Answer : Sizing SGA after adding extra memory

You need to do that with the root account - - Your System Admin should do that.

However, Oracle's recommendation for solaris 2.6 kernal parameters
(this is all taken from the Oracle8 Server installation guide for SPARC Solaris 2.6):
set shmsys:shminfo_shmmax=33554432 or higher to max sga size
set shmsys:shminfo_shmmin=1      (min value)
set shmsys:shminfo_shmmni=100  (min value)
set shmsys:shminfo_shmseg=10   (min value)
set shmsys:shminfo_semmni=70  (min value)
set shmsys:shminfo_semmsl=   set minimum equal to sum of # of PROCESSES in all init.ora files.
set shmsys:shminfo_semmns=200  (min value)
set shmsys:shminfo_semopm=100   (no oracle recommendation)
set shmsys:shminfo_semvmx=32767     (no oracle recommendation)
======================================

The parameter you are most interested in is  SHMMAX
I've seen shops shmmax = real memory on the server.  

Here is a typical system file on one of our E450 general servers,  2GB main memory, 4 CPU (450Mhz)  
using solaris 2.6 -- apx 10 development databases with variable # of users
------------------------------
set shmsys:shminfo_shmmax=107741824
set shmsys:shminfo_shmmin=1
set shmsys:shminfo_shmseg=200
set shmsys:shminfo_shmmni=1024
set semsys:seminfo_semmap=60
set semsys:seminfo_semmni=1600
set semsys:seminfo_semmns=2000
set semsys:seminfo_semmnu=1600
set semsys:seminfo_semume=80
set semsys:seminfo_semmsl=2000
set semsys:seminfo_semopm=100
set semsys:seminfo_semvmx=32767
------------------------------------------------------------------------------------------------------------
Other than that,  the rest of the /etc/system  parameters in the above example should be fine for you to use with the system you describe....

As far as the other general comments --  I do basically agree with the Idea that the sum of the all SGAs running on that server should probably not consume more than 50% of real memory (as a rule of thumb --  the size of the SGA can be increased to a higher ratio (ie: 60% to 75%)  depending upon certain things -- like are you using MTS?    small number of users will concurrently connect to the database in dedicated server mode, etc, etc)...

Hope this helps
dBalaski