SLU-initiated session with DLUS and DLUR within different subnetworks

Figure 1. SLU-initiated session with DLUS and DLUR within different subnetworks (part 1 of 2)

Figure 2. SLU-initiated session with DLUS and DLUR within different subnetworks (part 2 of 2)

The SLU initiates a Logon, which ENa encapsulates on the CPSVRMGR pipe and sends to VTAM1. VTAM1 sends a response to the Logon request followed by USS MSG0. Ena sends a response to USS MSG0 to VTAM1.
before initiating a search to locate the PLU, VTAM1 examines its cache. The PLU is located and is cached as being accessible through BNb. Because ENa is in a different subnet than VTAM1, no endpoint TGVs were reported over the CPSVRMGR pipe. Because the PLU is also within a different APPN subnet, VTAM1 will set the DSR indicator on the Locate request. VTAM1 will also set the DSL indicator on the Locate request because the SLU is a DLUS-served LU.
BNb caches the location of the SLU as being on ENa with VTAM1 as the NNS. The OCR indicator will not be set in the cache entry. BNb has the PLU cached as being accessible through BNc.
BNb modifies the Find resource hierarchy to indicate itself as the NNS(OLU) and adds a CV X'40' with VTAM1 as the MSCP. BNb also adds its endpoint TGs to the Locate search request and forwards the request to BNc.
BNc caches the location of the SLU as being on BNb. The OCR indicator is not set within the cache entry.
BNc has the location of the PLU cached as being within the native subnet. Because both the DSL indicator and the DSR indicator are set on the Locate request, BNc must obtain the SLU TGVs to be included on the Locate search request.

To obtain the endpoint TGVs, BNc initiates a Locate search to find the SLU. This search will be a PLU-init Search-Only. The OCR indicator is set, requesting that the DLUR node respond to the Locate request. The DSR indicator will not be set, because BNc is the node which is performing the extra Locate search.
BNb receives the new Locate search from BNc. BNb finds a cache entry for the SLU with the OCR indicator set. The entry indicates that BNa is the NNS(SLU), so BNb forwards the Locate search to BNa.
BNa also finds a cache entry for the SLU with the OCR indicator set. The cache entry for BNa indicates that the search should be forwarded to NNb.
NNb receives the Locate search from BNa. As part of its search logic, NNb will send either a directed Locate search to NNa or will perform a network broadcast that will ultimately reach NNa. Either way, the Locate search will be forwarded to NNa and, ultimately, ENa.
The OCR indicator is set, so ENa responds to the Locate. Because the SLU is a DLUS-served LU, ENa sets the DSL indicator on the reply. When building the reply, ENa will include a CV X'40' that includes the DLUS node CP name.
NNb caches the location of the SLU as being on ENa, with NNa as the NNS. NNb then calculates an RSCV for the Bind route between BNa and ENa and returns the RSCV to BNa.
BNa caches the location of the SLU as being on ENa, with NNb as the NNS. Because both the DSL and OCR indicators are set on the Locate reply, BNa sets the OCR indicator within the cache entry.
BNa modifies the Found resource hierarchy to indicate itself as the NNS(DLU). BNa then removes the RSCV from the Locate reply and places the NNb TGVs on the reply. The reply is then returned to BNb.
BNb caches the location of the SLU as being on ENa with BNa as the NNS. Both the DSL and OCR indicators are on the Locate reply, and BNb sets the OCR indicator on the reply. BNb then modifies the resource hierarchy in the reply to indicate itself as the NNS(DLU). BNb also replaces the NNb TGs with its own TGs and then forwards the reply to BNc.
BNc caches the location of the SLU as being on ENa with BNb as the NNS. Because both the DSL and OCR indicators are set on the Locate reply, BNc sets the OCR indicator within the cache entry.
BNc then takes the endpoint TGVs that were returned on the Locate reply that was just received from BNb and places the TGVs on the Locate request that was received from BNb. BNc then modifies the resource hierarchy on the request to indicate itself as the NNS(OLU). The search request is then sent to NNc.
NNc forwards the search request to ENb.
Because this is a SLU-init search request and an RSCV was not present on the Locate request, ENb initiates a PLU-init search with the SLU as the target.
NNc correlates the PLU-init search request with the outstanding SLU-init search request. Using the information that was provided on the original SLU-init search, NNc calculates an RSCV and returns it to ENb on the Locate reply. ENb then BINDs the session between the PLU and the SLU.
Because NNc creates the Locate reply instead of VTAM1, neither the DSL indicator nor the DSR indicator will be set on the reply. This can be contrasted to the original SLU-init request in which the DSL indicator was set.