IBM eServer zSeries 900 Technical Guide

98 IBM eServer zSeries 900 Technical Guide

The term FICON represents the architecture as defined by the InterNational Committee of

Information Technology Standards (INCITS), and published as ANSI standards. FICON also

represents the names of the z900 server features: FICON Express and FICON. Throughout

this section we will use the term FICON to refer to the FICON Express and FICON features,

except when the function being described is applicable to FICON Express only.

3.4.1 Description

FICON provides all the strengths of ESCON while increasing the link data rate from 20 MBps

all the way up to 2 Gbps with the FICON Express features. The FICON implementation

enables full-duplex data transfer, so data travels in both directions simultaneously, rather than

the half-duplex data transfer of the ESCON implementation. Also, FICON enables multiple

concurrent I/O operations to occur simultaneously to multiple control units, rather than the

sequential I/O operations of ESCON.

A FICON channel is capable of supporting significantly more I/O operations per second than

an ESCON channel. Also, data rate droop is minimal, even at distances of 100 km, compared

to ESCON’s significant data rate droop at distances greater than 9 km.

Another fundamental difference with ESCON is the Channel Control Word (CCW) chaining

capability of the FICON architecture. While ESCON channel program operation requires a

Channel End/Device End (CE/DE) after execution of each CCW, FICON supports CCW

chaining.

On a FICON channel, all CCWs of a chain are transferred to the control unit without waiting

for the first command response (CMR) from the control unit or for a CE/DE after each CCW

execution. The device presents a DE to the control unit after each CCW execution. If the last

CCW of the CCW chain has been executed by the device, the control unit presents CE/DE to

the channel.

The FICON channel architecture is compatible with:

򐂰 The Fibre Channel Physical and Signaling standard (FC-PH) ANSI X3.230-1994

򐂰 The Fibre Channel Switch Fabric and Switch Control Requirements (FC-SW) ANSI

X3T11/Project 959-D/Rev 3.3

򐂰 The FC-SB2 (FICON) architecture (INCITS standard)

FICON modes

The current z900 server support allows the FICON channel to operate in one of three modes:

1. A FICON channel in FICON Bridge (CHPID type FCV) mode can access ESCON control

units through a FICON Bridge port feature installed in a IBM 9032 Model 005 ESCON

Director; see Figure 3-10.

Figure 3-10 FICON bridge mode

FICON Bridge

FICON

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9032-5

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ESCON

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FCV

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ESCON

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FC Link

Chapter 3. Connectivity 99

2. A FICON channel in FICON native (CHPID type FC) mode can access FICON native

interface control units either:

– Directly via a FICON channel in FICON native point-to-point topology.

– Via a FICON channel in FICON native switched point-to-point topology connected to a

Fibre Channel switch (FC switch).

– Via a FICON channel in FICON native switched point-to-point topology connected to

cascaded Fibre Channel Directors (FC switches). See “FICON Support of Cascaded

Directors” on page 102.

Figure 3-11 FICON Native mode

A FICON channel in a FICON Channel-to-Channel (FCTC) configuration can access

FICON CTC control units and devices defined to different LPAR images on the same z900

server and other servers.

The FICON CHPID type is defined as a FICON native channel (FC). The FC channel at

each end of the CTC connection has a FICON CTC control unit (type FCTC) and FICON

CTC devices (type FCTC) defined.

The FICON channel at each end of the FICON CTC connection, supporting the FCTC

control units, can also communicate with other FICON native control units, such as disk

storage devices and tape.

“FICON channel-to-channel (FCTC)” on page 108 covers this connectivity in more detail.

3. A FICON channel in Fibre Channel Protocol (CHPID type FCP) mode can access FCP

devices either:

– Via a FICON channel in FCP mode through a single Fibre Channel switch or multiple

switches to an FCP device

– Via a FICON channel in FCP mode through a single Fibre Channel switch or multiple

switches to a Fibre Channel-to-SCSI bridge

FICON Native point-to-point

FICON Native Switched point-to-point

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