下面是MSDN關于SYS.dm_hadr_instance_node_map 的解釋，我就不在翻譯了

For every instance of SQL Server that hosts an availability replica that is joined to its AlwaysOn availability group, returns the name of the Windows Server Failover Clustering (WSFC) node that hosts the server instance. This dynamic management view has the following uses:

•This dynamic management view is useful for detecting an availability group with multiple availability replicas that are hosted on the same WSFC node, which is an unsupported configuration that could occur after an FCI failover if the availability group is incorrectly configured. For more information, see Failover Clustering and AlwaysOn Availability Groups (SQL Server).

•When multiple SQL Server instances are hosted on the same WSFC node, the Resource DLL uses this dynamic management view to determine the instance of SQL Server to connect to.

舉例來說

Env

===

Nodes:

SQL108W2K8R21

SQL108W2K8R22

SQL108W2K8R23

Default instance

SQL Server 2012 SP1 RTM

Availability group ：agTest1 and agTest2

AGTest1:

SQL108W2K8R21

SQL108W2K8R22

SQL108W2K8R23

AGTest2:

SQL108W2K8R21

SQL108W2K8R22

那么SYS.dm_hadr_instance_node_map 返回值如下

相應的ag_resource_id我們可以從sys.dm_hadr_name_id_map找到

DMV SYS.dm_hadr_instance_node_map會從下面的注冊表中取值

如果您的DMV返回NULL,請檢查注冊表HKEY_LOCAL_MACHINE/Cluster/HadrAgNameToIdMap，如果發現有legacy/orphan的鍵值存在，將他們刪除。為了以防萬一，請先備份。

之后再次運行DMV就可以了