Oracle online backup questions

    I am currently doing a survey of online database techniques in use by major database management systems. Can anyone tell me what facilities Oracle has for making a backup of a database while updates are still being applied to the database ?

    Does the online backup require transaction quiescence ?     Does it require update quiescence ?
    What sort of degradation of the transaction throughput     can be expected for the time during the backup when the     transactions are not quiesced ?

    Any information on this topic would be greatly appreciated.

Ted Heaven                        e-mail: heaven_at_bnr.ca
Bell Northern Research            phone: (613) 765-4650