Visara LINCS Configuration - Manual (Page 69)

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Chapter 3. Line Options
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SDLC/DAP Hardware Requirements
SDLC/DAP is supported on the SCC and HSC card for downstream connections. With the
SCC card, group polling is only supported when LINCS is attached to an FEP (LINCS is a
secondary station). With the HSC, LINCS supports group polling as a primary or secondary
station. Primary stations require configuring each downstream (secondary) connection on the
Gateway Circuit panels.
The number of remote lines that are supported by the SDLC/DAP feature is dependent upon
the following:
• Model of the 1174/9300 (see the Hardware Reference manual for your model)
• Number of physical host connections (see the Maximum Connections Limitations table)
• Whether lines are run half duplex or full duplex
• Which board is used: SCC or HSC
SDLC/DAP Software Requirements
Since support for DSPUs on an SDLC line is a gateway function, feature memory is required
to support SDLC/DAP.
See Feature Memory Allocation for more details on Feature memory.
The DAP Feature Activation Disk is required to run SDLC/DAP on some LINCS nodes.
How SDLC/DAP works
LINCS maintains the host sessions to the DSPU devices in much the same way that it supports
token ring DSPUs on the channel, by acting as a PU gateway. When the LINCS node is
channel attached, or attached via an HSC card, all DSPUs existing on the remote SDLC lines
appear as channel attached PUs to the host. In a similar fashion, if the DAP LINCS node is
LAN attached, the DAP LINCS node and all of its DSPUs appear as DSPUs to the gateway
(FEP TIC or channel attached control unit gateway).
When the host link is to be LAN attached to a FEP, the PUID for the downstream device must to
match the IDNUM in the VTAM Switched Major Node definition for the device. The PUID can
be configured in the downstream device, or configured on the Gateway Circuit for each
downstream PU, by specifying PUID Override (see Gateway Circuit 04 for an explanation of
PUID Override). This PUID (XID) is sent upstream by LINCS over the token ring or Ethernet
host link. The FEP will use this value to match the device to a VTAM definition. If there is no
match, there will be no connection. If another type of gateway exists upstream, such as another
LINCS node, this XID will not be used (unless the upstream gateway is a LINCS node and the
LU to PU mapping feature is present).
PUID Override is also used to gateway to downstream nodes that don’t support Test or XID
frames.
LINCS with the SDLC DAP feature will maintain all PU sessions with the host as if it were
the box that the host is attempting to contact (spoofing). It will keep inbound and outbound
queues for all DSPU devices that it supports. By conducting itself in this manner, DSPUs will