The communication relationship between a DDM source system and DFM is shown in Figure 1.

Figure 1. DDM Source System for z/OS Target Communication Flow

The DDM source system accesses z/OS® data using DFM as follows:

1. An application on the source system requests data.
2. The source LDMI (local data management interface) determines if the data is located locally or remotely.
3. If the data is remotely located, the request is turned over to the source DDM (DDM source).
4. An LU 6.2 to LU 6.2 network link is established between APPC LU 6.2 on the source system and VTAM® and APPC LU 6.2 on the z/OS system.
5. Source DDM sends an allocate request across the network link to DFM.
6. If the source is authorized access, a network conversation begins between source DDM and target DFM that processes remote data access to z/OS data.