# Prerequisites for RMAN backups
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Before backing up your database using the `rdsadmin.rdsadmin_rman_util` package, make sure that you meet the following prerequisites:
+ Make sure that your RDS for Oracle database is in `ARCHIVELOG` mode. To enable this mode, set the backup retention period to a non-zero value.
+ When backing up archived redo logs or performing a full or incremental backup that includes archived redo logs, and when backing up the database, make sure that redo log retention is set to a nonzero value. Archived redo logs are required to make database files consistent during recovery. For more information, see [Retaining archived redo logs](Appendix.Oracle.CommonDBATasks.RetainRedoLogs.md).
+ Make sure that your DB instance has sufficient free space to hold the backups. When back up your database, you specify an Oracle directory object as a parameter in the procedure call. RMAN places the files in the specified directory. You can use default directories, such as `DATA_PUMP_DIR`, or create a new directory. For more information, see [Creating and dropping directories in the main data storage space](Appendix.Oracle.CommonDBATasks.Misc.md#Appendix.Oracle.CommonDBATasks.NewDirectories).

  You can monitor the current free space in an RDS for Oracle instance using the CloudWatch metric `FreeStorageSpace`. We recommend that your free space exceeds the current size of the database, though RMAN backs up only formatted blocks and supports compression.