About Vendor Change Tracking
Several NAS storage array vendors have a difference engine that identifies the list of changed files and directories between two snapshot copies of the same volume. When Vendor Change Tracking (VCT) is enabled for a D-NAS policy, NetBackup does not perform any file system tracking for backup of NAS volumes. Instead it relies only on the change-list from the difference engine of the storage array to perform backup of files and directories. This process optimizes the backup process.
To use this feature, ensure that the storage that array provides this capability. D-NAS policy supports VCT enabled backups and index operations for Dell EMC PowerScale (Isilon), NetApp, Nutanix Files, and Qumulo NAS arrays.
VCT is not applicable in the following conditions:
Full schedule is only supported when accelerator is enabled along with VCT.
The base snapshot is not available.
Expire after copy retention option is selected for the snapshot in SLP.