Use volume append mode to create WORM appendable files


Starting with ONTAP 9.3, you can use the SnapLock volume append mode (VAM) feature to create WORM appendable files by default. A WORM appendable file retains data written incrementally, like log entries. Data is appended to the file in 256 KB chunks. As each chunk is written, the previous chunk becomes WORM-protected. You cannot delete the file until the retention period has elapsed.

What you’ll need
  • The WORM appendable file must reside on a SnapLock volume.

  • The SnapLock volume must be unmounted and empty of Snapshot copies and user-created files.

About this task

Data does not have to be written sequentially to the active 256 KB chunk. When data is written to byte n×256KB+1 of the file, the previous 256 KB segment becomes WORM-protected.

If you specify an autocommit period for the volume, WORM appendable files that are not modified for a period greater than the autocommit period are committed to WORM.


VAM is not supported on SnapLock audit log volumes.

  1. Enable VAM:

    volume snaplock modify -vserver SVM_name -volume volume_name -is-volume-append-mode-enabled true|false

    For a complete list of options, see the man page for the command.

    The following command enables VAM on volume vol1 of SVMvs1:

    cluster1::>volume snaplock modify -vserver vs1 -volume vol1 -is-volume-append-mode-enabled true
  2. Use a suitable command or program to create files with write permissions.

    The files are WORM appendable by default.