you are good, I never thought I should check alert file
here are tons of error in alert and 2 trace file:

ORA-12012: error on auto execute of job 9
ORA-02394: exceeded session limit on IO usage, you are being logged off
ORA-06512: at "SYS.DBMS_DEFER_SYS", line 2883
ORA-06512: at line 1
*** SESSION ID:(9.37413) 2001.02.02.14.42.50.000
*** 2001.02.02.14.42.50.000
ORA-12012: error on auto execute of job 10
ORA-02394: exceeded session limit on IO usage, you are being logged off
ORA-06512: at "SYS.DBMS_DEFER_SYS", line 2883

looks like I have problem for IO usage, how to solve it?
I am on SCO unixware 7.1, oracle 8.0.5

Jim