BUS-TECH 40-01459-D0-001, Руководство по установке

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ESCON Configuration 15
Chapter 4. ESCON C
ONFIGURATION
Figure 4-1. ESCON Attached Controllers
Overview
ESCON controllers, including the PCI ESCON Adapter (PBSA), can be connected to
the mainframe in more than one fashion. As shown in Figure 4-1, Controller 1 is
attached directly to one of the mainframe’s ESCON channels. Assuming the
mainframe is running a single Logical Partition (LPAR), this is simplest option for
connecting an ESCON controller to the mainframe. However, connecting an ESCON
controller directly to a mainframe’s ESCON channel in this fashion imposes two
restrictions:
1. Only a single controller can be attached to a mainframe’s channel.
2. The controller is only able to communicate with a single mainframe, the one it
is physically attached to.
An ESCON director overcomes these restrictions by attaching multiple “downstream”
controllers and by supporting multiple ESCON interfaces to multiple mainframes. In
Figure 4-1, Controllers 2 – 4 are connected to the director which is then connected to
two ESCON channels, one on each of two mainframes.
Some mainframes also support multiple, Logical Partitions (LPARs) running on a
single system; logically making the system appear as multiple computers. The
ESCON Multiple-Image Facility (EMIF) can be used in those environments to allow
sharing of ESCON channel paths across partitions. In Figure 4-1, a single channel
path defined between the mainframe and Controller 5 can be shared by both LPAR P1
and LPAR P2 using EMIF.