An Oracle ACFS snapshot is an online, read-only, point-in-time copy of an Oracle ACFS file system.
The snapshot copy is initially sparse and merely references the storage allocation information maintained by the file system.
Before an Oracle ACFS file extent is modified or deleted, its current value is copied to the snapshot using a copy-on-write (COW) technique to maintain the snapshot’s point-in-time view of the file system.
ACFS snapshots provide a low-cost way to preserve the state of a volume at a point in time. When a snapshot is created, a set of metadata about the volume is created in the same volume.
This metadata includes the directory structure and the names of all the files.
The snapshot consists of pointers to blocks in the volume that have not changed since the snapshot was created and the actual blocks if the file has changed.
After the snapshot is created, data blocks are written to the snapshot as files change, but only the original version of changed blocks are written. The snapshot allows you to recover deleted files, revert files to the version at the time of the snapshot, and back up a consistent file set by taking a backup of the snapshot.
Can be used to:
Managing ACFS Snapshots
The snapshot copy is initially sparse and merely references the storage allocation information maintained by the file system.
Before an Oracle ACFS file extent is modified or deleted, its current value is copied to the snapshot using a copy-on-write (COW) technique to maintain the snapshot’s point-in-time view of the file system.
ACFS snapshots provide a low-cost way to preserve the state of a volume at a point in time. When a snapshot is created, a set of metadata about the volume is created in the same volume.
This metadata includes the directory structure and the names of all the files.
The snapshot consists of pointers to blocks in the volume that have not changed since the snapshot was created and the actual blocks if the file has changed.
After the snapshot is created, data blocks are written to the snapshot as files change, but only the original version of changed blocks are written. The snapshot allows you to recover deleted files, revert files to the version at the time of the snapshot, and back up a consistent file set by taking a backup of the snapshot.
Can be used to:
- Revert to a version in the snapshots
- Recover a deleted file
- Back up a consistent data set
- Are limited to 63 snapshot views per volume
Managing ACFS Snapshots
Create snapshots:
$ acfsutil snap create snapshot_2 /u01/app/oracle/acfsdata/testvol
Delete snapshots:
$ acfsutil snap delete snapshot_2 /u01/app/oracle/acfsdata/testvol
$ acfsutil snap delete snapshot_2 /u01/app/oracle/acfsdata/testvol
View file system information, including snapshots:
$ acfsutil info fs <mount point> ls –l <mount_point>/.ACFS/snaps
$ acfsutil info fs <mount point> ls –l <mount_point>/.ACFS/snaps
This comment has been removed by the author.
ReplyDeleteHi Sunil, i was going through Oracle ACFS. How is it different from the normal FTP server? I searched a lot , but couldn't find how to read and write files to this Oracle ACFS. If you could throw some light on this, it would be helpful for me.
ReplyDeleteThank You.