Locate resource: Complex APPN network using more than one CDS

Figure 1. Locate resource: Complex APPN network using more than one CDS (part 1 of 2)

Diagram of locate resource: Complex APPN network.

Figure 2. Locate resource: Complex APPN network using more than one CDS (part 2 of 2)

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 its resource information 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.
The subarea SSCP replies that the target resource is not known.
NN1 has no APPN-domain end nodes; therefore, no domain broadcast occurs. NN1 does not initiate a network broadcast because there is a central directory server (CDS) in the network. NN1 sends a request to CDS1.
CDS1 receives the request and performs origin CDS logic. CDS1 looks in its directory database for the target resource and does not have an entry. Therefore, the APPN control point (CP) requests the location of the resource from the subarea SSCP.
The subarea SSCP replies that the target resource is not known.
CDS1 has no domain end nodes; therefore, no domain broadcast occurs. CDS1 begins an alternate CDS search by sending a request to CDS2.
CDS2 looks in its directory database for the target resource and does not have an entry. The APPN 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.
CDS2 has no domain end nodes to which to send a domain broadcast. Therefore, CDS2 returns a negative reply to CDS1.
CDS1 continues the alternate CDS search by sending a request to CDS3.
CDS3 looks in its directory database and finds an entry that indicates that the target resource resides on NN3. CDS3 replies to CDS1 with this information.
CDS1 sends a request to NN3 to verify that the target actually resides there.
NN3 replies to CDS1 that it does, indeed, own the target resource.
CDS1 returns a reply 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 returns a reply to the end node.