The following methods are valid for backing-up an Oracle database:
Export/Import - Exports are "logical" database backups in that they
extract logical definitions and data from the database to a file.
Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files.
Hot or On-line Backups - If the databases are available and in
ARCHIVELOG mode, set the tablespaces into backup mode and backup
their files. Also remember to backup the control files and archived redo
log files.
RMAN Backups - While the database is off-line or on-line, use the
"rman" utility to backup the database.
It is advisable to use more than one of these methods to backup your
database. For example, if you choose to do on-line database backups,
also cover yourself by doing database exports. Also test ALL backup
and recovery scenarios carefully. It is better to be save than sorry.
Regardless of your strategy, also remember to backup all required
software libraries, parameter files, password files, etc. If your database
is in ARCGIVELOG mode, you also need to backup archived log files.