You must determine whether the data service ever needs to know the host name of the server on which it is running. If so, the data service might need to be modified to use a logical host name (that is, a host name configured into a logical host name resource that resides in the same resource group as the application resource), rather than that of the physical host.
Occasionally, in the client-server protocol for a data service, the server returns its own host name to the client as part of the contents of a message to the client. For such protocols, the client could be depending on this returned host name as the host name to use when contacting the server. For the returned host name to be usable after a takeover or switchover, the host name should be a logical host name of the resource group, not the name of the physical host. In this case, you must modify the data service code to return the logical host name to the client.