In addition to the existing checks, the new implementation has the following additional checks.
The new implementation stores and uses a historical snapshot of the database state information to decide if a failover should be initiated. The health check routine caches the database state and associated error information, for the last two executions, which is then compared with the state information from the current execution of the health detection routine. If the same error condition (for the below mentioned error codes) exists in three consecutive runs of the health detection routine, a failover is initiated. This implementation is intended to provide safeguards against transient errors and issues which can be fixed by the auto page repair capabilities of the availability groups.
The new implementation checks for following additional errors. Majority of these errors are indicative of a hardware issues on the server. Please note, that this is not an exhaustive list of errors which could impact the database availability. There is an outstanding item to include error 824 to this list.
Great news from the Tiger Team.