Setting isolation levels with Oracle V7

Is there a global parameter (or parameter file) where I can set the isolation level for a whole oracle instance, a database, table space, or table. I am runnin a series of experiments where the isolation level is a control parameter and I would prefer a system level setting of the isolation level as opposed to pre-declaring it at the beginning of each transaction.

Thanks
Dex

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Dexter P. Bradshaw                   \ Internet: dpbradsh_at_bluebox.uwaterloo.ca
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