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Normally, a dependent LU session requires a direct communications link to the host computer. If many nodes (including a host node) are connected together in an APPN network, some of them may not have a direct connection to the host, but only an indirect connection through another node. It is not possible to establish dependent LU sessions to the host from LUs in these indirectly connected nodes.
Dependent LU requester (DLUR) is an APPN feature designed to overcome this limitation.
This section explains how to configure a DLUR PU that provides connectivity to a host computer. Configuring a DLUR PU enables the local node to provide DLUR services.
DLUR on an APPN node (such as a node running SNAP-IX) works in conjunction with dependent LU server (DLUS) at the host, to route sessions from dependent LUs on the DLUR node across the APPN 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. DLUR must be available on the node where the LUs are located, and DLUS must be available on the host node, but DLUR is not required on any intermediate nodes in the session route.
If the SNAP-IX DLUR node is a network node, it can also provide passthrough DLUR facilities for dependent LUs on downstream computers connected to the SNAP-IX node. These LUs can 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.
To provide passthrough DLUR services to a downstream node, you must first configure (on the local node) the PU name associated with the downstream node. This value must match the PU name that is configured for the downstream node on the host computer.
To configure a DLUR PU, use one of the following methods:
Select Connectivity and New DLUR PU from the Services menu on the Node window.
Issue the following command:
define_internal_pu
The following parameters are required for DLUR PU configuration:
For each DLUR PU on the local node, specify a PU name. The name does not need to match the PU name configured on the host.
The fully qualified LU name of the host LU that supports DLUS.
In order to use DLUR, the DLUR component of SNAP-IX has to establish an LU-LU session with the DLUS on the host.
Contact your SNA network planner to determine the name of the host LU.
The PU ID of the PU on the local node that supports connectivity to the host. The PU ID comprises two hexadecimal strings, one of three digits (known as the block number), and one of 5 digits.
Each dependent LU is associated with a PU. Both the PU and the LU are configured on the host computer. For each PU, you need to define a DLUR PU on the SNAP-IX node. The PU ID must match the PU ID configured at the host for this PU.
In many cases the PU ID is the same as the node ID, so the node ID is the default. However, if you need more than 255 dependent LUs to access a specific host, you need to configure multiple DLUR PUs, each with up to 255 dependent LUs, and each with a different PU ID.
If you are not sure how to set this field, consult your SNA network planner.
In a VTAM configuration, the first three digits should match the IDBLK parameter in the PU definition, and the last five digits should match the IDNUM setting.
Whether the DLUR PU is to be activated automatically when the node is started. If you do not set this option, the DLUR PU must be started manually.
Whether the DLUR PU is to be activated automatically after a failure (once the cause of the failure has been remedied).
You need the following information in order to configure SNAP-IX to use passthrough DLUR to transport traffic between dependent LUs on downstream nodes and a host:
The PU name associated with the downstream node. The PU name must match the PU name configured on the host computer.
A downstream node can support multiple PUs. In this case, each downstream PU is associated with a different link, so you need to configure multiple links between the SNAP-IX DLUR node and the downstream node, and you need to know the downstream PU name for each link.
Consult your SNA network planner to find out the PU names associated with the downstream nodes.
The fully qualified LU name of the host LU that supports the DLUS. In order to use DLUR, the DLUR component of SNAP-IX has to establish an LU-LU session with the DLUS on the host.
Consult your SNA network planner to find out the LU name for the host DLUS server.
After configuring DLUR, continue with the following configuration tasks:
To configure LUs for DLUR, see Configuring DLUR.
To configure other passthrough services, see Configuring Passthrough Services.
To support specific user applications, see Configuring User Applications.
To support APPC communication, see Configuring APPC Communication.
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