This message will be sent when the controller sees a latent error in the backup Disk Configuration Block (DCB). A scrubbing activity will be started to repair any sector errors on getting this error. An effort is made to read the backup DCB even when the primary DCB is successfully read. When an error occurs here, this is a latent error that needs to be addressed before any future errors so this DCB is re-written with the primary copy to rectify the errors found.