Locate resource: Complex APPN network

Figure 1. Locate resource: Complex APPN network

The end node sends a search request for a target resource to the network node server. As network node server of the originating LU, NN1 looks for the target resource in the directory database. NN1 has no knowledge of the target resource in the directory database.
The APPN control point (CP) requests that the subarea SSCP check for information about the location of the resource.
The subarea SSCP replies that the target resource is not known.
Because NN1 does not have the target resource in either its APPN or subarea directories, it initiates a resource discovery search for the resource. Because the resource discovery search starts at the beginning of the search logic, another CACHE_SEARCH is performed. NN1 has no APPN-domain end nodes; therefore, no domain broadcast occurs.
The subarea SSCP replies that the target resource is not known.
NN1 does not initiate a network broadcast because there is a central directory server (CDS) in the network; therefore, NN1 sends a request to this CDS.
CDS1 receives the request and performs origin CDS logic. CDS1 looks in its directory database for the target resource and has an entry that indicates that the target resource resides on NN4. CDS1 sends the request to NN4.
NN4 owns the resource; therefore, NN4 returns a positive reply.
CDS1 replies to NN1.
Because the resource discovery search found the resource, NN1 sends a search to the target, containing the original session-specific information.
The target is found.
NN1 replies to the end node.