I have a Solaris server V445 running:
5.10 Generic_120011-14 sun4u sparc SUNW,Sun-Fire-V445

The server has 8G of memory. However TOP only is showing 700M
available.

The DB instance is only taking up approx 1G in shared memory segment,
i.e. SGA

GROUP CREATOR CGROUP NATTCH SEGSZ CPID LPID ATIME
DTIME CTIME
Shared Memory:
m 1 0x76125b4 --rw-r----- oracle dba oracle
dba 36 943734784

BY THE WAY ORACLE 10G:

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit
Production
With the Partitioning, OLAP and Data Mining options

SQL> select * from v$SGA;

NAME VALUE
-------------------- ----------
Fixed Size 2034632
Variable Size 486544440
Database Buffers 419430400
Redo Buffers 35708928

Why is the server only showing 700M free. I actually brought the
instance down due to perf issues today then viewed memory. When
instance was down it was showing 7+G of available memory. As soon as I
started the instance with no connections the memory immediately
dropped to 800M available.

Also before bringing instance down swap utilization was at 50% of
available, i.e. 4G out of 8G.

Curent TOP
Memory: 8192M phys mem, 762M free mem, 8193M total swap, 8193M free
swap

At least swap is not being used now.

What is eating up all the OS memory?

NOTE: There is another server running 2 9i instances with 8G of mem
and 3G in share memory for the 2 instances and this server show 3G
free mem.

Thanks.