How to find remote session executing over a database link

Follow this procedure to find remote session created by local session executing query over database link:

1-) Find local session id from v$session

2-) Execute following script on both local and remote databases:

Select /*+ ORDERED */
s.sid,substr(s.username,1,15),substr(s.ksusemnm,1,10)'-' substr(s.ksusepid,1,10) "ORIGIN",
substr(g.K2GTITID_ORA,1,35) "GTXID",
substr(s.indx,1,4)'.' substr(s.ksuseser,1,5) "LSESSION" ,
substr(decode(bitand(ksuseidl,11),1,'ACTIVE',0,
decode(bitand(ksuseflg,4096),0,'INACTIVE','CACHED'),
2,'SNIPED',3,'SNIPED', 'KILLED'),1,1) "S",
substr(w.event,1,10) "WAITING"
from x$k2gte g, x$ktcxb t, x$ksuse s, v$session_wait w ,v$session s
where g.K2GTDXCB =t.ktcxbxba
and g.K2GTDSES=t.ktcxbses
and s.addr=g.K2GTDSES
and w.sid=s.indx
and w.sid=s.sid
/

3-) From the script output on local database find GTXID value for local session
4-) From the script output on remote database, search for a GTXID value matches the one we find on step 3. When you find it, sid column of the same row is the session we are looking for on remote database.

Another method is using lsof (assuming it is a unix server)

1-) Find process id of the local session

select spid from v$session s ,v$process p where s.paddr=p.addr and s.sid={local_sid}

2-) On the server (running local database) find out TCP connections of the session

lsof -p {process id}

3-) Search for a line containing remote server name (or IP) in output of step 2. When you find it, take destination port number
4-) On remote server run following command to find oracle process listening on this port

lsof -i tcp:{port_number}

5-) Now you can find remote session by running following script on remote database:

select s.sid from v$session s ,v$process p where s.paddr=p.addr and spid={oracle_process_id}