Do you want to be able to recover your database (should it fail) to the point in time before it crashed? If so, you MUST use archive log mode. If not, then you can just go back to the last backup. In general archive log mode is recommended for all critical, high availability, can't lose the data type databases.

Alex

Further to the other reply, I would suggest that for a large database of
this nature, that ARCHIVELOG mode would be required.

With a large capacity, it will be highly unlikely that you could backup
the entire database in a single session, while the database is down,
which will be required for a cold backup. With ARCHIVELOG enabled
databases, backups (hot or cold) do not need to backup the entire
database in a single session.

Further, I would expect that some data will not be volatile, and
therefore needs to be backed up at a less frequent rate than that of the
volatile data. i.e. If you are in a DW environment for Paging or Mobile
phone systems, records are added to the current month, but previous
months are probably not modified, and therefore these tablespaces could
be made Read Only, and once backed up, there is no need to be backed up
on a regular basis.

You comment about the downgrade in performance, I would have thought
that this should not be a problem. I would expect that the alternate
Redo Log Groups would be placed on different disks, and that the Archive
Redo Logs would be on another set of disks. Therefore, when a Log Switch
occurs, and archival is initiated of the old Redo Log, the Archiver will
be accessing one set of disks, and the LGWR will be writing to the other
set of disks.

Hope this helps,
Andrew