SDNC Generic Resource API Concurrency and Async Support for Service, VNF and VF Module. 

The GR-API behavior today for all action works with a service content regardless of the action level Service Assign vs VNF Assign etc.. As a result of this behavior if concurrent request are sent or update to MD-SAL occur during the assignment for any of the action the data in MD-SAL overwritten as a result of parallel raise condition. If transaction 2 finish first then transaction 1 will overwrite with its context as an example. 

In addition to concurrency support, SO and GR-API are moving towards an ASYNC mechanism for only Service, VNF and VF module assign.