Configuring PU Concentration

Normally, a dependent LU session requires a direct communications link to the host computer. However, a node running SNAplus2 that has a direct communications link to the host can also provide PU concentration facilities to LUs on downstream computers, enabling them to access the host over the communications link from the SNAplus2 node. The downstream computer must contain an SNA PU type 2.0 or 2.1 to support dependent communication with the host. For example, the downstream computer could be another computer running SNAplus2 in a standalone configuration.

Using the PU concentration 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 can set up several downstream computers connected to SNAplus2 over a local token ring network, so that they all access the same long-distance SDLC leased line from SNAplus2 to the host.

Using PU concentration also simplifies the configuration at the host. The host configuration needs to include only 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.

Before configuring PU concentration, you must perform the following configuration tasks:

To enable PU concentration, you must configure LUs on the local node to support sessions with downstream workstations. (If you configured a template on the port to support implicit downstream LUs, you may not need to define downstream LUs explicitly.) The LUs defined on the local node are referred to as “downstream LUs.” To configure downstream LUs, you need the LU numbers that are used on the downstream nodes, and the name of the host LU. (The LUs that are defined on the downstream nodes can be any dependent LU type.)

To configure downstream LUs, use one of the following methods:

Downstream LU Configuration Parameters

The following parameters are required for downstream LU configuration:

Downstream LU name

A name for each downstream LU. The LU name is used only to identify the LU locally, and does not need to match any configuration on the downstream node.

If you are defining a range of LUs, specify a base name of 1-5 characters. SNAplus2 adds a three-digit decimal string to the base name to create an LU name for each LU number you specify.

Downstream PU name

The name of the link station to the downstream node.

LU number

The LU number must match the LU number defined on the downstream node. Contact your SNA network planner if you do not know what LU number to use.

You can configure several LUs with consecutive LU numbers by defining a range of LUs.

Upstream LU name

The name of the host LU or a pool of LUs with which the downstream LUs will communicate.

Fake logon

To reduce the number of LUs required, SNAplus2 displays a fake logon screen; a 3270 user must hit a key before the user is associated with an upstream LU.

Allow timeout

To reduce the number of LUs required, an LU without an active PLU-SLU session is disassociated from the upstream LU after this number of seconds.

Additional Configuration

After performing the downstream LUs for PU concentration configuration, continue with the following configuration tasks:

• To configure user applications, see Chapter 8 “Configuring User Applications”