Why a long transaction cannot rollback?? (2)

I test a long transaction in Online 5.0. Only one user in this Online. That is me. The long transaction is like this... begin work; update table1 set field1='1'; update table2 set field2='1'; update table3 set field3='1'; : : : update table50 set field50='1';commit work; I set LTXHWM=50 & LTXEHWM=60. When logical logs used 60%, this transaction began rollback. When rollback used the last logical log, many checkpoint happend. When the last logical log used 100%, "The logical logs are full---Backup is need." showed on the sys log file. No matter I used Auto-Backup or Continue-Backup, I still couldn't backup all full logical fogs. The Online 5.0 cannot work anymore. I thought this Online 5.0 got some problems with the AIX UNIX 3.2.5. So I test again on SCO UNIX whit Online 5.0, the same thing happen. Why???? It is a bug on Online 5.0? Or I cannot test like that? How can I test a long trancation and rollback normally? -- Madeline Wu from Taiwan.......