The below is the scrap of a trace when one of our user reported his session is hang.
The status of his session is INACTIVE.

SELECT DECODE(UPPER(:b1),'HTML','.RPT','PDF','.PDF','.RPT')
FROM
DUAL


call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 0 0.00 0.00 0 0 0 0
Execute 11 0.00 0.00 0 0 0 0
Fetch 11 0.00 0.00 0 33 0 11
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 22 0.00 0.00 0 33 0 11

Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 509 (xyuser)

Rows Execution Plan
------- ---------------------------------------------------
0 SELECT STATEMENT GOAL: CHOOSE
0 TABLE ACCESS (FULL) OF 'DUAL'


Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 22 0.00 0.00
SQL*Net message from client 21 1299.58 1499.63
********************************************************************************


Entries in V$session_wait is

SQL> select * from v$session_wait where sid=120;

SID SEQ# EVENT P1TEXT P1 P1RAW P2TEXT P2 P2RAW P3TEXT P3 P3RAW WAIT_TIME SECONDS_IN_WAIT STATE
---------- ---------- ---------------------------------------------------------------- ---------------------------------------------------------------- ---------- ---------------- ---------------------------------------------------------------- ---------- ---------------- ---------------------------------------------------------------- ---------- ---------------- ---------- --------------- -------------------
120 2158 SQL*Net message from client driver id 675562835 0000000028444553 #bytes 1 0000000000000001 0 00 0 279 WAITING



Refer to my previous post about the DUAL table. THe above post is same with more details. I could able to simulate the issue also.

Please advice what could be wrong.?
I could also take more information (as long as the user is using this module -- luckily now using).