> Start Oracle hot backups (2 at a time)  6am - 6pm

Oracle recommends that hot backups be done during periods of low update
activity because updates generate unusually large amounts of redo log data
during hot backups. When a database update occurs logging normally records
which fields are affected and how the fields are changed. When an update
occurs during a hot backup the 'after' version of every block affected by the
change is written to the redo logs. This allows the recovery process to bring
'fuzzy' backups of the .dbf files back to a consistent state. The size of a
block is between 1024 and 8192 bytes, depending on the configuration. Most of
the time you have earmarked for hot backups falls within the normal work day.
Are you sure you have the disk space and I/O bandwidth to support the
intensive logging associated with hot backups during the work day?