There may be many error messages shown on the CMDB Sync Status page, such as Remedy AR error 120006 and 120141.

In Discovery 11.2 and later, the CMDB Sync is "self-healing", and will recover automatically from many errors.  See KA 000143492.
Many/most of the errors can therefore be ignored.  

How does a customer know if something is really wrong with CMDB Sync?

First, it is not necessary to watch the CMDB Sync Status page for errors.  And, it should not be necessary to review the CMDB Sync logs to determine the health.

Here is a 4-step process for determining the health of CMDB Sync:

1) Check that the CMDB Sync connection is still working (i.e. the connection shows a green or orange banner in the UI).


2) Check that the queue is still processing, or if the queue is empty, then is it appropriate that it is empty.

3) Check the "Devices that failed last CMDB sync" report



4) When there are devices returned from the "Devices that failed last CMDB sync" report, determine if they are transient errors -vs- permanent errors, as follows:
       a) From the "Devices that failed last CMDB sync" report page, Select All, and Actions->CMDB Sync
       b) After those devices finish sync'ing, then run the report again.
       d) Devices that are no longer on the list only had transient failures.
            Devices that continue to be on the list may have permanent failures.  Open a customer support ticket to get help with these permanent failures.

If the connection is still working, the queue is processing or is correctly empty, and there are no permanent failures in the "Devices that failed last CMDB sync" report, then the CMDB Sync is healthy.