The subscriber and Cisco Unity server information (Digital Networking Data) fails to update on one Cisco Unity server. This can include any of these:
license pooling data
This causes Cisco Unity to go into license violation.
If the Global Catalog (GC) monitor (AvDsGlobalCatalog) can not contact its GC twice, it discovers a new GC with which to sync. Since Update Sequence Number (USNs) are not consistent across DC/GCs, when Cisco Unity connects to a new GC, it must complete a full resync in order to ensure proper synchronization.
When the GC monitor reconnects because of two failed connection attempts, the LastUSN value in the UnityDb configuration must be set to 0. But, at times this does not happen. if the GC that Cisco Unity reconnects with has a lower USN, this can cause a critical replication to fail, because Cisco Unity believes its data in SQL is more recent.