u should first check /etc/system
as tamils mentioned u should make sure if your os allows more than the number of processes mentioned..

I am enclosing the formula:

set shmsys:shminfo_shmmax=4294967295
set shmsys:shminfo_shmmin=1
set shmsys:shminfo_shmmni=100
set shmsys:shminfo_shmseg=10
set semsys:seminfo_semmni=100
set semsys:seminfo_semmsl=x
set semsys:seminfo_semmns=y
set semsys:seminfo_semopm=100
set semsys:seminfo_semvmx=32767

x = #of processes available (refer init<sid>.ora) plus 10 per instance.
As of now they are 100 processes plus 10 since it is 1 instance.
so x = 110

y = double the #of largest processes parameter available plus 10 per database.
As of now, 100 processes x 2 = 200 plus 10 per database
so y = 210

The above are 2 of the few parameters need to be set in the /etc/system file.
Log in as root and check to make sure the modifications suits your requirement.

Once u are done in Unix, then change the init.ora and bounce the db. I guess you should be all set..

I have another concern:
If I have 100 processes set, are even the 10 background processes included or excluded in the count..

Thanks