here is one qurey that caused so much sql*net wait:

********************************************************************************

<one select query involing outer join of two tables>

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      4      0.00       0.00          0          0          0           0
Fetch        4      0.00       0.00          0         68          0          32
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        9      0.00       0.00          0         68          0          32

Misses in library cache during parse: 0
Optimizer goal: CHOOSE
Parsing user id: 178

Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                       5        0.00          0.00
[B]  SQL*Net message from client                     4       16.01         27.14[/B]



below is overall total:
********************************************************************************

OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse       20      0.00       0.00          0          0          0           0
Execute     24      3.79       4.34          0      61385      20366       20006
Fetch        8      0.04       0.04          0        303          0          45
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total       52      3.83       4.39          0      61688      20366       20051

Misses in library cache during parse: 0

Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                     247        0.00          0.00
  SQL*Net message from client                   246       16.01         38.98
  log file sync                                  12        0.16          0.74
  db file sequential read                       854        0.05          0.39
  SQL*Net more data from client                6966        0.09          1.07
  direct path write (lob)                       431        0.32          0.46
  log file switch completion                      2        0.42          0.56
  SQL*Net more data to client                     1        0.00          0.00