The storage space inside the Exadata storage servers is configured for use by Oracle Automatic Storage Management (ASM) When you launch an Exadata Cloud Infrastructure instance.

By default, the following ASM disk groups are created:

• The DATA disk group is intended for the storage of Oracle Database data files.
• The RECO disk group is primarily used for storing the Fast Recovery Area (FRA), which is an area of storage where Oracle Database can create and manage various files related to backup and recovery, such as RMAN backups and archived redo log files.
• The /acfs file systems contain system files that support various operations. You should not store custom files, Oracle Database data files, or backups inside the ACFS disk groups. Custom ACFS mounts can be created using the DATA ASM disk group for files that are not service-related.

The disk group names contain a short identifier string that is associated with your Exadata Database machine environment. For example, the identifier could be C2, in which case the DATA disk group would be named DATAC2, the RECO disk group would be named RECOC2, and so on.

In addition, you can create a SPARSE disk group. A SPARSE disk group is required to support Exadata snapshots. Exadata snapshots enable space-efficient clones of Oracle databases that can be created and destroyed very quickly and easily. Snapshot clones are often used for development, testing, or other purposes that require a transient database.

Note that you cannot change the disk group layout after service creation.

• Impact of Configuration Settings on Storage
  Your choices concerning database Backups or sparse disk groups profoundly affect how storage space in the Exadata storage servers is allocated to the ASM and sparse disk groups