SNAplus2 Resources

Dependent LU Register (DLUR)

This section does not apply to LEN nodes.

As well as providing direct access to a host computer, SNAplus2 can also provide DLUR facilities. This feature enables sessions for dependent LUs to span multiple nodes in an APPN network, instead of requiring a direct connection to the host.

DLUR on the SNAplus2 node works in conjunction with Dependent LU Server (DLUS) at the host to route sessions from dependent LUs on the SNAplus2 node across the network to the DLUS host. The route to the host can span multiple nodes, and can take advantage of APPN’s network management, dynamic resource location, and route calculation facilities.

PU Concentration

As well as providing direct access to a host computer, SNAplus2 can also provide PU concentration facilities. This feature enables other computers to use SNAplus2 resources to access a host computer instead of requiring a separate connection to the host from each computer.

Figure 1-2 illustrates the PU concentration feature.

Figure 1-2 PU Concentration Facilities Provided by SNAplus2

The downstream computer must contain an SNA PU type 2.0 or 2.1 to support dependent LUs. For example, the downstream computer could be a PC running Microsoft’s SNA Server for Windows NT or another SNAplus2 computer.

Using this feature, all the data transferred between the host and the downstream computer is routed through the SNAplus2 local node. This enables a downstream computer to share a host connection with SNAplus2 or with other downstream computers instead of requiring a direct link. For example, you could set up several downstream computers connected to SNAplus2 over a local Token Ring network, so that they could all access the same long-distance leased line from SNAplus2 to the host.

Using PU concentration also simplifies the configuration at the host because there is no need to define the downstream computers and the communications links to them. The host configuration only needs to include the SNAplus2 computer and its host communications link; the LUs at the downstream computers are configured as part of the resources of the SNAplus2 computer. The host computer is not aware that PU concentration is being used.

TN Server

SNAplus2 TN server provides access to 3270 host computers for TN3270 users on other computers. The TN server feature enables TN3270 users to share a host connection with SNAplus2 or with other TN3270 users, instead of requiring a direct link. It also enables TN3270 users to access hosts that are not running TCP/IP.

Figure 1-3 illustrates the SNaplus2 TN server function.

Figure 1-3 SNAplus2 TN Server

The SNAplus2 TN server feature provides an association between a TN3270 user and SNAplus2 3270 LU. All data from the TN3270 user is routed to the LU. This means that the configuration for both the host and the TN3270 user is as though they were connected directly; neither needs to be aware that data is being routed through TN server.