You can perform basic backup and recovery tasks using operating system utilities and standard SQL commands.
However, there are several drawbacks to using these so-called user-managed backup and recovery techniques.
For example, you cannot perform incremental backups
using user-managed techniques. In general, user-managed backup and recovery techniques require you to manually keep track of your backup files, their status, and their availability.
You must write your own SQL and operating system scripts to manage the backup and recovery operations. In addition, you must provide the necessary data files and archived log files during a database recovery operation. If the database is operating during your backups (online or hot backups), you must place the database files in the backup mode before performing the actual file backups.
Oracle explicitly states that you can use user-managed techniques to perform backup/recovery activities.
Oracle actually states that both user-managed techniques and RMAN are alternative ways of performing backup and recovery tasks.
However, Oracle strongly recommends using RMAN to make your backups and perform database
recovery, because of the tool’s strengths and powerful features. Although you can perform a basic backup and recovery task with user-managed techniques without ever having to even start the RMAN interface, you should make RMAN your main backup and recovery tool for several reasons.
Several important backup and recovery features are available to you only through RMAN.