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After the initial (full) VM backup or replication, all consequent job runs are forever incremental.
By default, NAKIVO Backup & Replication uses the VMware CBT technology to identify what which data has changed since the last job run.
Several factors – such as a power outage – can cause VMware CBT to reset and lose a track of the incremental changes for a VM. 
The above error message appears in case when the CBT error handling is set to reset CBT and automatic CBT reset fails.
 For more information on CBT, see VMware KB 1020128.


  1. Check .vmx file of the VM and make sure that the following options are present:
    ctkEnabled = "TRUE"
    scsi0:0.ctkEnabled = "TRUE"
    NOTE: if the VM has multiple disks, this option must be present for each disk.
  2. Check the VM folder on the datastore. Make sure that there is the -CTK.VMDK file for each disk.

If any of the above conditions is are not met, reset CBT as follows: