Specifications

Logical paths and path groups
A logical path is a connection between a controller image and a host image. An
ESCON link consists of two fibre-channels. There is a fibre-channel for each
direction. An ESCON connector connects the fibre-channel port to an ESCON.
Each ESCON adapter card supports two ESCON ports or links. Each port supports
64 logical paths. With a maximum of 32 ESCON ports, the maximum number of
logical paths is 2048.
Each controller image supports up to 64 path groups. Each path group might have
up to eight logical paths. Each controller image supports a maximum of 128 logical
paths.
Cable lengths and path types
All ESCON attachments have a light-emitting diode (LED) interface. The cable
attached to the host adapter can be up to 2 km (1.2 mi) in length using 50-µm fibre
or 3 km (1.9 mi) in length for 62.5-µm fibre. There are no cable splices inside the
ESS. Laser links or LEDs can exist between the host system attached to the:
v Storage server and the host channel controller
v Peer controller host channel
v Peer controller with appropriate equipment
Note: Appropriate retention hardware to support cable attachments that control
bend-radius limits comes with each ESCON host attachment.
Data transfer
The ESCON host adapter supports all data input buffer sizes up to 256 bytes.
During write operations, the host adapter requests the minimum pacing count of hex
XX'02X'. For commands whose parameter data length is not determined by the
parameter data itself, the full transfer count in the command frame is requested in
the first data request. The adapter supports an NDF-R count of 7 (that is, a
maximum of eight data requests).
Directors and channel extenders
The ESS supports IBM ESCON directors 9032 Models 1, 2, 3, and 5. The ESS
supports IBM 9036 channel extenders to the distances that are allowed by the 9036
as described in “Cable lengths and path types”. The ESS supports the 9729
Wavelength Division Multiplexer channel extender up to 50 km (31 mi).
Identifying the port for TSO commands
Figure 39 on page 72 helps you identify the port ID for the MVS TSO commands for
S/390 and zSeries hosts. The numbers like 806, 804, 802, and 800 are internal
microcode numbers. The numbers like 00, 04, 08, and 0C are tag numbers. You
need tag numbers for the path setup. To determine the tag number, use the deserv
command with the rcd (read configuration data) parameter.
Chapter 7. Attaching to an IBM S/390 or IBM eServer zSeries host 71