IBM Z9, Руководство по планированию

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Shared Channel Overview
MIF allows channels to be shared among multiple LPs. Shared channels are
configured to an LP giving the LP a channel image of the shared channel that it can
use. Each channel image allows an LP to independently access and control the
shared channel as if it were a physical channel assigned to the LP.
By providing the logical equivalent of multiple physical channels dedicated to
multiple LPs, a shared channel can reduce hardware requirements without a
corresponding reduction in I/O connectivity. This reduction in hardware requirements
can apply to physical channels, Director ports, and control unit ports, depending on
the configuration.
MIF Requirements
To take advantage of MIF, you need:
v An ESCON-capable operating system:
– z/OS
– z/VM
– z/VSE
– AIX/ESA
®
– TPF
– z/TPF
v ESCON channels operating in native mode (CNC) or channel-to-channel mode
(CTC), FICON channels attached to an ESCON director (FCV), FICON channels
(FC), coupling facility channels (ICP, CBP, CIB, or CFP), open systems adapter
channels (OSC, OSD, OSE or OSN), internal queued direct communication
(HiperSockets) channels (IQD), and fibre channel protocol channels (FCP).
Note: ESCON channels that attach to a 9034 ESCON Converter Model 1 (CVC
or CBY) cannot be shared among LPs.
v
IBM ESCON-capable or FICON-capable control units, or fibre channel switches.
Understanding ESCON and MIF Topologies
This section describes the following I/O topologies:
v
Point-to-point topology
v
Switched point-to-point topology
v
MIF channel sharing topology
Point-to-Point Topology: The traditional point-to-point topology requires a unique
path between any two points that communicate. A channel and CU adapter are
required between each communication point. In a point-to-point configuration, a
channel can communicate with only one control unit. A control unit that
communicates with more than one channel requires a separate control unit adapter
interface to each channel. The configuration limitations in a point-to-point topology
can lead to inefficient use of channels and control units. See Figure 2-8 on page
2-22 for an example of the point-to-point topology.
Switched Point-to-Point Topology: Switched point-to-point topologies eliminate
the disadvantages of point-to-point and multidrop topologies. Switched point-to-point
topology enables switching between any channel path and control unit adapter
when using an ESCON or FICON Director. By using the Director, paths can also be
shared by multiple points. The Director enables one channel to switch to multiple
control units, or one control unit to switch to multiple channels. Paths necessary to
satisfy connectivity requirements in a point-to-point topology are not required in the
switched point-to-point topology. This can reduce the number of channels and
Chapter 2. Planning Considerations
2-21
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