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The resources of the SNAP-IX system can be divided into two types:
Define the communications capabilities of a particular APPN node:
Connectivity resources:
DLCs
Ports
Link stations
Connection networks
LUs
Type 0-3 for:
3270
RJE
LU0 communications
LUA communications
Type 6.2 for:
APPC
CPI-C communications
5250 emulation
Modes and classes of service
Directory information
Additional resources not defined as part of the node, which are used to support particular user programs. These resources include:
3270 user information
RJE workstations
CPI-C side information
Information about access to the UNIX Command Facility and Service Point Command Facility
For more information about these resources, refer to the SNAP-IX Administration Guide.
This section does not apply to LEN nodes.
As well as providing direct access to a host computer, SNAP-IX 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 SNAP-IX node works in conjunction with Dependent LU Server (DLUS) at the host to route sessions from dependent LUs on the SNAP-IX 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.
If the local node is a network node, dependent LUs on downstream computers connected to the SNAP-IX node can also use DLUR on the SNAP-IX node to access the host across the network, in the same way as for LUs internal to the node.
As well as providing direct access to a host computer, SNAP-IX can also provide PU concentration facilities. This feature enables other computers to use SNAP-IX resources to access a host computer instead of requiring a separate connection to the host from each computer.
PU Concentration Facilities Provided by SNAP-IX, illustrates the PU concentration feature.
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 SNAP-IX computer.
Using this feature, all the data transferred between the host and the downstream computer is routed through the SNAP-IX local node. This enables a downstream computer to share a host connection with SNAP-IX or with other downstream computers instead of requiring a direct link. For example, you could set up several downstream computers connected to SNAP-IX over a local Token Ring network, so that they could all access the same long-distance leased line from SNAP-IX 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 SNAP-IX computer and its host communications link; the LUs at the downstream computers are configured as part of the resources of the SNAP-IX computer. The host computer is not aware that PU concentration is being used.
SNAP-IX 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 SNAP-IX 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.
SNAP-IX TN Server, illustrates the SNAP-IX TN server function:
The SNAP-IX TN server feature provides an association between a TN3270 user and SNAP-IX 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.
Any 3270 emulation programs that communicate over TCP/IP rather than over an SNA network are referred to as TN3270 programs (Telnet 3270 emulation programs). SNAP-IX TN server supports various TN3270 programs, including SNAP-IX TN3270 (packaged separately from the main SNAP-IX product).
When a TN3270 program communicates with TN server, SNAP-IX identifies
it by the TCP/IP address of the computer where the TN3270 program is running;
it cannot distinguish between two different TN3270 programs being used by
different users on the same computer. In the SNAP-IX manuals, the term
TN server user
refers to the computer where a TN3270 program is running
(identified by its TCP/IP address), and not to an individual user of that
program.
Each TN server user is normally configured to access a single 3270 LU and so is restricted to one host session at a time. However, you can also configure a TN server user to access a pool of 3270 LUs instead of having a single dedicated 3270 LU for each user. This enables the user to access as many sessions as there are available LUs in the pool.
You can also define a default record that enables access by any TN3270 client (with the same LUs or LU pools for all clients), instead of having to define an individual record for each client.
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