dbawiki

If your database is running out of processes, increase the value along with sessions and transactions. But spare a thought for the PGA.

select max(p.pga_max_mem)/1024/1024 "PGA max process (MB)"
from   v$process p
,      v$session s
where  p.addr = s.paddr
and    s.username is not null;

PGA max process (MB)
--------------------
          142.203085

This shows the maximum amount of PGA used by an active process.
Now work out the total possible amount that could be used by the new value of processes.

select name
,      value
from   v$parameter
where  name = 'processes';

NAME                 VALUE
-------------------- ----------
processes            4000

So 140Mb * 4000 is about 560Gb which is a lot! So either a lot more space (may) be needed for the PGA or the processes need to come down.
As an aside, this gets the total SGA:

select sum(value)/1024/1024 "Total SGA (MB)" from v$sga;