SQL & PL/SQL

Hi,
I have used global temp table on commit preserve rows.
During initialization of the screen i'm creating temp tables and all the manipulation done on
screen has been stored on temp table ,
at the end of all the insert and delete operation i'm retrieving it from temp table and displaying
it in the screen,at some point of time the temp table value is lost.So nothing is been displayed in
screen.
I tried to find out the problem according to me the session got expires coz of that the value in
the temp table becomes empty and last value inserted is stored.Is there any other option to retain the value throughout the session
can anyone help me out to solve this problem it will be great to get a help.

syntax

CREATE global temporary TABLE #TMP_TABLE# on commit preserve rows AS SELECT #ORG_TABLE#.*

retreiving

SELECT column1.A,column2.A, column3.A FROM #TMP_TABLE#.A