Visara CCA-3074 Planning Guide - Manual (Page 20)

Chapter 2. Planning for Your Installation
2-6 707159-002
Replacing Existing ESCON 3174 Controllers
Each of your existing 3174 Non-SNA controllers is capable of
communicating to only one LPAR, and appearing as only one
control unit image (CUI). Each 3174 is therefore utilizing only
one CUADD of the 16 CUADD values that can be defined (0-F)
through a single ESCON or FICON interface. It is common to use
the same CUADD number for each 3174 (if no CUADD
parameter is found in the CNTLUNIT macro of the gen,
CUADD=0 is implied). The CCA-3074 provides support for
multiple CUIs, allowing it to replace multiple 3174 controllers.
To replace multiple 3174s with a single CCA-3074, even if they
have ESCON interfaces, you will normally have to make some
minor gen changes to direct the connection to the CCA-3074.
Replacing Bus and Tag Controllers
Bus and Tag definitions and ESCON definitions are different, so
you will always require Gen changes when replacing Bus and Tag
controllers with a CCA-3074. A CCA-3074 with a single
ESCON interface can replace up to 16 Bus and Tag controllers, or
up to 32 controllers with two ESCON interfaces.
Determining the Need for Directors
If you have more than two mainframe platforms or have multiple
LPARs on a single mainframe that does not support EMIF/MIF,
or if you are running multiple logical channel subsystems (LCSS)
on a single mainframe, you will probably be best served by using
ESCON and FICON directors. Directors allow multiple LPARs
and multiple mainframes to communicate to a CCA-3074 through
a single interface (up to 16 CU images). If Directors are to be
used, consider implementing a redundant Director to eliminate a
single point of failure.
When to Use EMIF/MIF
If your mainframe supports EMIF (Enterprise Multiple Imaging
Facility) or MIF (Multiple Imaging Facility) and you are running
multiple LPARs, making use of EMIF/MIF can greatly reduce the
number of interfaces by allowing multiple LPARs (up to 15) to
share a single channel.