SQL> select b.sid, b.serial#, a.spid processid, b.process clientpid from v$process a, v$session b
where a.addr = b.paddr
and b.audsid = userenv(‘sessionid’);
SID SERIAL# PROCESSID CLIENTPID
———- ———- ——— ———
43 52612 420734 5852:5460
V$SESSION.SID and V$SESSION.SERIAL# are database process id
V$PROCESS.SPID – Shadow process id on the database server
V$SESSION.PROCESS – Client process id, on windows it is “:” separated the first # is the process id on the client and 2nd one is the thread id.
An Oracle Spin by Alex Lima 
improvment :
>> and b.audsid = userenv(‘sessionid’);
and s.audsid = SYS_CONTEXT (‘userenv’, ‘sessionid’);