performance tuning problem

Hi, everyone:

I have a strange problem: I have an Oracle 8i database running in W2K server ( only 256M RAM, that's low) with a very large table called Table1 ( about 4 millions records). I issued a SQL query at that table in the server machine , like
SQL> select col1 from table1 where col1='value1';

It takes about 2 minutes or so. But if I open two sessions simultaneously and issue the same query like above , the performance is dynamically dropped, it takes about 20 minutes or more to finish.

TIA Received on Mon Jul 01 2002 - 18:22:19 CDT