Oracle RAC 10g - maximum number of session exceeded

You are going to have to look at the semaphore kernel parameters as well.  I didn't see that in the link that was posted.  Unless something has changed and Oracle does something special (like it does with memory segments), you are going to need enough semaphores to support 1000 sessions.  It is likely the parameters can already handle that, but you need to check.

Thanks alot experts for your comments
this is the semaphore kernel parameters:
semaem                            16384  Default
semmni                             4200  4200
semmns                             8400  8400
semmnu                             4196  (nproc-4)
semmsl                             2048  Default         Immed
semume                              100  Default
semvmx                            32767  Default
shlib_debug_enable                    0  Default         Immed
shmmax                       8589934592  8589934592      Immed
shmmni                              512  512             Immed
shmseg                              300  Default         Immed

can you check it.
I dont have experience in kernel parameters.
Also what is the best way to change the parameters
Change processes parameter only or change processes and sessions and transaction all.