RMAN can create backups on disk as image copies or as backup sets.

You can override this default with the AS COPY or AS BACKUPSET clauses.

BACKUP AS COPY DEVICE TYPE DISK DATABASE;

BACKUP AS BACKUPSET DATABASE;

BACKUP AS BACKUPSET DEVICE TYPE DISK DATABASE;

BACKUP AS BACKUPSET DEVICE TYPE SBT DATABASE;

You can use FROM TAG to copy an image copy with a specific tag, and then use TAG to assign the output copy a different tag.

E.G. creates new copies of all image copies of the database that have the tag full_cold_copy and gives the new copies the tag new_full_cold_copy.
BACKUP AS COPY COPY OF DATABASE FROM TAG full_cold_copy TAG new_full_cold_copy;

Views to Identify Multisection Backups

Use the MULTI_SECTION column of the V$BACKUP_SET view or the recovery catalog view RC_BACKUP_SET to determine if a backup is a multisection backup. For multisection backups, the MULTI_SECTION column contains the value YES.

Views That Contain Metadata for Multisection Backups

The V$BACKUP_DATAFILE and RC_BACKUP_DATAFILE views provide information about the number of blocks in each section of a multisection backup. The BLOCKS column specifies the number of blocks in each multisection backup.

Making Multisection Backups Using Image Copies

RMAN enables you to create multisection backups using image copies.

Multisection backups provide better performance by using multiple channels to back up large files in parallel. Starting with Oracle Database 12c Release 1 (12.1), you can create multisection full backups that are stored as image copies. While the image copy is being created, multiple channels are used to write files sections. However, the output of this operation is one copy for each data file.
Use the SECTION SIZE clause to create multisection backups. If the section size that you specify is larger than the size of the file, then RMAN does not use multisection backups for that file. If you specify a small section size that would produce more than 256 sections, then RMAN increases the section size to a value that results in exactly 256 sections

BACKUP AS COPY SECTION SIZE 500M DATABASE;

About Manual Backups of the Control File

A manual backup of the control file is different from a control file autobackup.

RMAN makes a control file autobackup after the files specified in the BACKUP command are backed up. Thus, the autobackup—unlike a manual control file backup—contains metadata about the backup that just completed. Also, RMAN can automatically restore autobackups without the use of a recovery catalog.

You can make a manual backup of the current control file either as a backup set or as an image copy. For a backup set, RMAN first creates a snapshot control file for read consistency. You can configure the file name and location of the snapshot control file. A snapshot control file is not needed for an image copy.

In an Oracle Real Application Clusters (Oracle RAC) environment, the following restrictions apply:
■The snapshot control file location must be on shared storage—that is, storage that is accessible by all Oracle RAC instances.
■The destination of an image copy of the current control file must be shared storage.