Oracle ASM File System (ACFS) is a file system implemented within ASM.
It allows you to store almost anything you can imagine within ASM, such as files and backups, including even database executables. In more advanced options and with large architectures, you can use it to take snapshots and clones with Exascale Volumes, use it with Oracle , snapshots in Exadata, etc.
The only thing that should not be stored in ACFS the root directory of the Grid Infrastructure or any Oracle file Oracle can be stored directly in Oracle ASM.
This document describes how to create an ACFS use it as a backup.
In our case, we are going to create the ACFS file within one of the disk groups already created. We will choose the FRA disk group to create the ACFS perform the backup on that mount point.
You can create a new diskgroup (recommended), e.g., with the name ACFSDG, and create the ACFS file ACFS the newly created diskgroup.
Here is an example of how to do it.
acfs
Keep in mind that the space you are using is ASM space, so you are using space from the disks assigned to that disk group, with all that that entails. That is why it is recommended to create a new disk group. In our case, since this is a test environment, we will do it on an existing disk group.
We load the ASM environment variables ASM check the available space with the lsdg command.
From the 20G available in the disk group "FRA," column "Usable_file_MB," we are going to create a 5Gb ASM file system (ACFS).
- Create an Oracle volume on a disk group mounted with ASM.
We will use the volcreate command to create a volume in the ASM disk group, in our case FRA.
oracle> asmcmd
ASMCMD> volcreate -G FRA -s 5g volume1
2. Displays information about Oracle volumes.
We verify that the volume has been created correctly.
ASMCMD> volinfo -G FRA volume1
Diskgroup Name: FRA
Volume Name: VOLUME1
Volume Device:asm
State: ENABLED
Size (MB): 5120
Resize Unit (MB): 64
Redundancy: MIRROR
Stripe Columns: 8
Stripe Width (K): 1024
Usage:
Mountpath:
It is important to verify the disk volume in this case: asm. We will use it for the next step.
3. Create a new ACFS file system
With the root user, we execute the following:
oracle> /sbin/mkfs -t acfs asm
mkfs.acfs: version = 21.0.0.0.0
mkfs.acfs: on-disk version = 50.0
mkfs.acfs: volume =asm
mkfs.acfs: volume size = 5368709120 (5.00 GB)
mkfs.acfs: file system size = 5368709120 (5.00 GB)
mkfs.acfs: Format complete.
4. Mount the ASM File System.
We create the /backup directory, change its owner to oracle mount the ASM file system.
root@localhost ~]# mkdir /backup
[root@localhost ~]# chown oracle:oracle
[root@localhost ~]# /bin/mount -t acfs asm/backup
4. Register the file system in the clusterware.
This step is very important because it will cause ACFS automatically ACFS the mount point, in our case /backup. This prevents the mount point from failing to mount automatically after a reboot, which would result in it being inaccessible.
/sbin/acfsutil registry -a asm /backup
5- Verify that the file system has been created.
With the ASM environment variables, you can check with theASM view that the volume has been created correctly.
Using the crs command, we verify that the acfs volume acfs correctly registered in the cluster.
oracle21dg> crsctl status res -t
ora.fra.volume1.acfs
ONLINE ONLINE oracle21dg mounted on /backup,STABLE
ONLINE ONLINE oracle22dg mounted on /backup,STABLE
We can now use the ACFS system. In our case, we will use it to perform backups directly in ASM.
We connect to the database and create the directory to perform the export on the new ACFS /backup).
SQL>create directory EXPORT as '/backup';
Directory created.
We launch the export.
oracle> expdp system/oracleconraul@test schemas=system directory=EXPORT dumpfile=exp_system.dmp logfile=exp_system .log
Export: Release 21.0.0.0.0 – Production on Mon Dec 1 16:16:23 2025
Version 21.3.0.0.0
Copyright (c) 1982, 2021, Oracle its affiliates. All rights reserved.
Connected to: Oracle 21c Standard Edition 2 Release 21.0.0.0.0 – Production
Starting "SYSTEM.""SYS_EXPORT_SCHEMA_01": system/@test schemas=system directory=EXPORT dumpfile=exp_system.dmp logfile=exp_system.log
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Processing object type SCHEMA_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS
Processing object type SCHEMA_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
