Oracle 8i, SuSe Linux, big performance problem whith hot backup

Hello,
i have a very interisting problem on SuSe Linux 7.0 (or 7.1). Engine: Fujitsu Siemens Primargy, 4 Processors, 4 GB RAM I want to make a hot backup.
After i set the tablespace in backup mode i make a copy of the tablespace. On that moment goes nothing more with Oracle. There is no input/output from/to the database. (Every select needs extremly long time)
Have anybody an idea? (I hope so)
What is the break?
Oracle or SuSe Linux?

There is an important detail:
The load average goes from 0.4 (0.X) up thru 5.X (at that moment i must kill the job)

Thanks and bye

Michael

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mailto: michael.hermanns_at_gmx.de