Oracle7 hot backups / table availability

This is posted for a friend.

   I have heard that a "hot backup" of an oracle7 database means    the file is "quiescent". What does this mean ?

   I am planning to use oracle7 in a high availability environment.    I must be able to access the tables for update while they are    being backed up, and still have good backup. Is this a problem ?

   Also, does anyone have any information of backup/recover times    for a ~20Gig database ? The platform will be a UNIX server, the    specific server hardware has not yet been selected.

   Thanks in advance for any help.

--
Davide Gaetano
sysdfg_at_gsusgi2.gsu.edu