Below is the script to find the respective sid of an server proccess id.
col sid format 999999
col username format a20
col osuser format a15
select b.spid,a.sid, a.serial#,a.username, a.osuser
from v$session a, v$process b
where a.paddr= b.addr
and b.spid='&spid'
order by b.spid;
SEE ALSO - Get ospid from sid
ospidsid DATABASE SCRIPTS