Download Subchannel Number - Der z9 Mainframe der Universität Leipzig

Datenverwaltung, Ein-/Ausgabe
it-Akademie Bayern
z/OS und OS/390 Lehrgang 2008
Prof. Dr.-Ing. Wilhelm G. Spruth
Teil 8
Adressierung des Ein-/Ausgabe Subsystems
EA 0701 ww6
 copyright W. G. Spruth, 08-2004
wgs 10-02
Adressierung im
Ein-/Ausgabe Subsystems
IBM zSeries Connectivity Handbook
International Technical Support Organization, May 2003
SG24-5444-03
f:\grx\redbooks\connect1.pdf
Devices
System z verwendet den Begriff “Device”, eine
Abkürzung für I/O Device.
Typische Devices sind




Plattenspeicher (DASD, Disk Drive),
Magnetbänder,
Drucker,
..........
Heute werden fast ausschließlich logische DASDs
vom Typ 3390 eingesetzt. Diese werden von einem
Enterprise Storage Subsystem (ESS) auf regulären
3 ¼ Zoll Platten emuliert.
Devices werden von einem System mit Hilfe eines
Device Identifiers adressiert
Early system design
The DASD (disk drive) marked with an X has address 132,
derived as shown below
8 Bit
8 Bit
Device Address
The disk drive marked with an Y can be addressed
as 171, 571, or 671 because it is connected through
three channels. By convention the device is known
by its lowest address (171), but all three addresses
could be used by the operating system to access the
disk drive.
Multiple paths to a device are useful for performance
and for availability. When an application wants to
access disk 171, the operating system will first try
channel 1. If it is busy (or not available), it will try
channel 5, and so forth.
Shown is another S/360 system with two channels
connected to control units used by the first system.
This sharing of I/O devices is common in all
mainframe installations. Tape drive Z is address A31
for the first system, but is address 331 for the
second system.
Current mainframes use a different approach.
In the good old S/360 days, a device address such
as 583 meant channel 5, control unit 8, device 3 and
this was the address of the device. No S/390
machines work this way today, but the old
terminology is often used. This terminology is
technically incorrect, but is so widely used that you
must understand it. If someone tells you to “IPL
from address 583” they really mean to IPL from
device number 583.
For all S/390 machines, the hardware address of a
device will be something like chipd 05, CU 3, UA 7.
This is similar to the old S/390 addresses; a chpid is
a channel, the CU number is a control unit address,
and the UA is a unit address (that can normally
range up to x’FF’). However, the software never sees
this hardware address. The S/390 I/O subsystem,
using the IOCDS data, converts the chpid/CU/UA
“hardware address” into a device number. The
operating system uses the device number to
connect to I/O devices. The operating system and
applications never see the actual hardware
addresses (the chpid, CU, and UA numbers).
Historische Entwicklung
Parallel-I/O-interface
For a channel path of the parallel-I/O-interface type,
the device identifier is called a device address (unit
address) and consists of an eight-bit value.
ESCON-I/O interface
For the ESCON-I/O interface, the device identifier
consists of a four-bit control-unit address and an
eight-bit unit address .
FICON-I/O interface
For the FICON-I/O interface, the device identifier
consists of an eight-bit control-unit-image ID
(address) and an eight-bit unit address.
The unit address (device address) identifies the
particular I/O device (and, on the parallel-I/Ointerface, the control unit) associated with a
subchannel.
E/A Konfigurations-Netzwerk
Channel Subsystem
Hauptspeicher
CPU
CPU
CPU
FF ... FF
Benutzer
Prozesse
Ke r n e l
SAP
SAP
00 ... 00
HSA
CH.
CH.
CH.
CH.
Kanäle
Channel
Subsystem
CU
CU
CU
CU
CU
CU
CU = Control Unit
Plattenspeicher
Das Channel Subsystem wird durch mehrere Prozessoren (als
System Assist Prozessoren, SAP, bezeichnet) und entsprechenden
Code verwirklicht. Die SAPs greifen parallel zu den CPUs auf den
Hauptspeicher zu und entlasten diese von Ein-/Ausgabe Aufgaben.
Die HSA (Hardware System Area) ist ein Teil des Hauptspeichers.
Sie liegt außerhalb des Adressenraums, auf den die CPUs zugreifen
können. Das Channel Subsystem besteht aus SAP Prozessoren und
Code in der HSA. Es bildet das virtuelle E/A Subsystem, mit dem
der Betriebssystem Kernel glaubt zu arbeiten, auf die reale E/A
Struktur ab.
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Hauptspeicher
CPU
Kanal
256
Devices
pro
Kanal
max.
Kanal
Kanal
256
Kanäle
max.
Kanal
Kanal
CU
CU
CU
CU
CU
CU
CU
CU
CU
CU
S/390 Device Identifikation
0
78
15
16 Bit I/O Address
Channel Device
Address Address
max. 256 Channels und max. 256 Devices pro Channel
Heutige Konfiguration
Die früheren parallelen Kanäle wurden durch serielle
ESCON und FICON Kanäle ergänzt. Letztere werden
gemeinsam als „Channel Path“ bezeichnet und
durch eine 8 Bit Channel Path ID (CHPID) or physical
channel identifiers (PCHIDs) gekennzeichnet. Ein
Channel Subsystem kann maximal 256 Channel Path
unterstützen.
Auf eine Control Unit kann über unterschiedliche
Channel Path zugegriffen werden,
Heutige Konfiguration (3)
Eine Ein/Ausgabe Einheit (Device), z.B. ein Plattenspeicher,
wird eines 16 Bit Device Identifiers angesprochen. Für
FICON besteht dieser aus einer 8 Bit Control Unit Nr. und
einer 8 Bit Device Address. Letztere wird auch als Unit
Address bezeichnet.
0
78
16 Bit
Device Identifier
Control
Unit Nr.
Device
Address
15
Auszug aus
z/Architecture
Principles of Operation (1)
One subchannel is provided for and dedicated to
each I/O device accessible to the channel subsystem.
Up to 256 I/O devices can be addressed on a single
parallel-I/O interface.
Up to 256 devices can be attached to each control
unit that uses the serial-I/O interface
The channel subsystem provides information about
associated I/O devices to CPUs, which obtain this
information by executing I/O instructions. The actual
number of subchannels provided depends on the
model and the configuration; the maximum
addressability is 65,536.
The maximum addressability of channel paths
provided by a channel subsystem is 256.
Auszug aus
z/Architecture
Principles of Operation (2)
A device identifier is an address, not apparent to the
program, that is used by the channel subsystem to
communicate with I/O devices. The type of device
identifier used depends on the specific channel-path
type and the protocols provided.
Each subchannel contains one or more device
identifiers. For the FICON-I/O inter-face, the device
identifier consists of an eight-bit control-unit-image
ID and an eight-bit device address.
Identifikation von Fritz Müller
Normalerweise:
Fritz Müller
geb. 21. Juni 1985
Geburtsort Augsburg
Vater Staat benutzt statt dessen für die deutsche
Rentenversicherung eine Nummer, z.B.:
970 63210685S048 11
die Fritz Müller eindeutig identifiziert.
Identifikation von Fritz Müller
System z Devices
Normalerweise:
Fritz Müller
geb. 21. Juni 1985
Geburtsort Augsburg
Device Nr.
Vater Staat benutzt statt dessen für die deutsche
Rentenversicherung eine Nummer, z.B.:
970 63210685S048 11
Device Identifier
die Fritz Müller eindeutig identifiziert.
Heutige Konfiguration (1)
4 Begriffe:
Channel Path ID (CHPID)
Subchannel Number
Device Nr. (1 pro Subchannel)
Device Identifier
8 Bit
16 Bit
16 Bit
16 Bit
Der Device Identifier besteht aus einer
8 Bit Control Unit Address und einer
8 Bit Device Address.
Die 8 Bit Device Address wird häufig auch als Unit
Address bezeichnet und ist nicht zu verwechseln mit
der 16 Bit Device Nr.
Subchannel
A subchannel provides the logical appearance of a
device to the program and contains the information
required for sustaining a single I/O operation.
The subchannel consists of internal storage (UCW)
that contains information in the form of a
 CCW address,
 channel-path identifier,
 device number,
as well as additional Information like count, status
indications, and I/O-interruption sub-class code,
path availability and functions pending or being
performed.
I/O operations are initiated with a device by executing I/O instructions that designate the
subchannel associated with the device.
Subchannel Number
A subchannel number is a system-unique 16-bit
value used to address a subchannel. The
subchannel is addressed by eight I/O instructions:








CANCEL SUBCHANNEL,
CLEAR SUBCHANNEL,
HALT SUBCHANNEL,
MODIFY SUBCHANNEL,
RESUME SUBCHANNEL,
START SUBCHANNEL,
STORE SUBCHANNEL, and
TEST SUBCHANNEL.
Each I/O device accessible to the channel
subsystem is assigned a dedicated subchannel at
installation time. All I/O functions relative to a
specific I/O device are specified by the program by
designating the subchannel assigned to the I/O
device.
Normally, subchannel numbers are only used in
communication between the CPU program and the
channel subsystem.
START SUBCHANNEL
Machine Instruction
When START SUBCHANNEL is executed,
parameters are passed to the target subchannel
requesting that the channel subsystem perform a
start function with the I/O device associated with the
subchannel. The channel subsystem performs the
start function by using information at the subchannel, including the information passed during
the execution of the START SUBCHANNEL
instruction, to find an accessible channel path to the
device. Once the device has been selected,
execution of an I/O operation is accomplished by the
decoding and executing of a CCW by the channel
subsystem and the I/O device.
Am operation-request block (ORB) is designated by
a START SUBCHANNEL instruction.
Subchannel Number
 Device identification used for communication
between z/OS and channel subsystem
 16 Bit, 65 536 possible devices
 Index for the UCW table (Unit Control Word table)
within the HSA.
 Used by microcode during execution of the SSCH
(Start Subchannel) machine instruction
 Stored in the UCB at IPL time
 Independent of device number
 Used for communication between I/O Supervisor and
Channel Subsystem (CSS)
UCW Table
UCW
UCW
Subchannel Number
Each device is identified to
 humans by a 16- bit device number
 the Channel Subsystem by a 16- bit subchannel
number
Subchannel Number
A subchannel number is a system-unique 16-bit
value used to address a subchannel. The subchannel is addressed by eight I/O instructions, e.g
START SUBCHANNEL.
Each I/O device accessible to the channel
subsystem is assigned a dedicated subchannel at
installation time. All I/O functions relative to a
specific I/O device are specified by the program by
designating the subchannel assigned to the I/O
device.
Normally, subchannel numbers are only used in
communication between the CPU program and the
channel subsystem.
The Channel subsystem uses a Device Identifier to
communicate with a particular device.
z/OS
Adressenraum
des Kernels
Channel
Subsystem
HSA
UCB
UCW
Subchannel
Nr.
Device
Nr.
Unit Address
(Device Address)
Unit Control Block (UCB)
Unit Control Word (UCW)
Der Unit Control Block (UCB) wird vom
Betriebssystem unterhalten. Er enthält die
Subchannel Nr. und die entsprechende Device Nr.
Das Unit Control Word (UCW) wird vom Channel
Subsystem unterhalten. Er enthält die Device Nr.
und die entsprechende Unit Address
Device Number
Each subchannel that has an I/O device assigned
to it also contains a system-unique parameter
called the device number. The device number is
a 16-bit value that is assigned as one of the
parameters of the subchannel at the time the
device is assigned to the subchannel.
The device number provides a means to identify a
device, independent of any limitations imposed by
the system model, the configuration, or channelpath protocols. The device number is used in
communications concerning the device that take
place between the system and the system operator.
For example, the device number is entered
by the system operator to designate the input
device to be used for initial program loading.
Any operator command that refers to a device uses
the device number.
The subchannel number is assigned to the subchannel
(UCW) representing the device at POR time. It indicates the
relative position of the UCW in the UCW table. The specific
value depends on the position of the statement I/O DEVICE
in the Input/Output Configuration Program (IOCP).
It is used to reference the device during the communication
between z/OS and the channel subsystem as well as during
execution of the SSCH instruction and during interrupt
processing. The subchannel number was designed to
speed up the search of a UCW during the SSCH
processing. The same device accessed by different logical
partitions has one UCW per image.
The subchannel number is expressed in a 16-bit value,
whose valid range is 0000-FFFF, allowing for a maximum of
65,536 devices per z/OS image. Stored in the UCB at IPL, it
is not declared during Hardware Configuration Definition.
Unit address
The unit address (UA) or device address is used to
reference the device during the communication between a
channel and the control unit serving the device. The UA is
two-hex digits in the range 00-to-FF stored in the UCW as
declared in HCD, and it is transmitted over the I/O interface
to the control unit by the channel.
Each parallel channel supports the full unit address range
of 00-to-FF and so allows connection of up to 256 devices.
For an ESCON interface, architecturally the control unit
supports the full unit-address range of 00-to-FF and may
support up to 256 devices.
Mapping subchannel number
in unit address
The UCB has all the information needed for the
preparation of the SSCH instruction by IOS,
including the subchannel number.
The subchannel number is used by the channel
subsystem to find the UCW in its UCW Table.
A device identifier (for FICON an 8 bit control unit
address plus 8 bit unit address) is an address, that
is used (not apparent to the program) by the channel
subsystem to communicate with I/O devices. The
channel subsystem, will find in the UCW the receiver
address (link, control unit, and unit address) to be
sent over a FICON or ESCON connection.
Any operator command that refers to a device uses
the device number.
Device number
The device number is a kind of nickname for the device. It
is assigned at HCD creation by the installation. It is used to
reference the device during the communication between
z/OS and human beings, as well as in messages and
console commands, JCL, RMF device reports, and at IPL to
indicate the SYSRES device.
A device number is contained in a 16-bit value field, whose
valid range is 0000-FFFF, which allows for a maximum of
65,536 devices. The device number is stored in the UCW
table (within the HSA) at power-on reset (POR) and in UCB
at IPL. UCW represents the device from the channel
subsystem point of view; a UCB represents the device from
the I/O Supervisor (IOS) point of view.
8 Bit Control Unit Nr. 8 Bit Unit Address
= Device Address
0
78
15
16 Bit FICON Device Identifier
The Unit Address (UA) has no relationship to the device
number or the subchannel number for a device. During
Hardware Configuration Definition (HCD) the unit address
frequently defaults to the last two digits of the device
number, if not explicitly specified.
The unit address defined in HCD must match the unit
address on the control unit where the device has been
physically installed by the hardware service representative.
In the example, the operator issues the V PATH command
for device number 2004. A separate I/O operation must be
started for each device. The device number 2004
corresponds to the UA 04 and this is the address that the
channel sends to the control unit
In summary, the device number is used in communication
between an operator and z/OS; the subchannel number is
used in communication between z/OS and channel
subsystem; and the unit address is used in communication
between the channel and the control unit.
Channel-Path Identifier
The channel-path identifier (CHPID) is a systemunique eight-bit value assigned to each installed
channel path of the system. A CHPID identifies a
physical channel path device, independent of any
limitations imposed by the system model, the
configuration, or channel-path protocols.
A device can be accessed over one of several
channel path. The device identifier is thus unrelated
to the channel path identifier.
Ein-/Ausgabe Steuerblöcke
Anwendungsprogramm
DCB
DEB
UCB
Data Control Block
Data Extend Block
Unit Control Block
Access Method
IOB
ECB
Input/Output Block
Event Control Block
I/O Driver, z.B. EXCP
SRB
IOSB
System Request Block
Input/Output Supervisor
Control Block
IOS
UCB
IOQ
ORB
IRB
PSA
HSA
Unit Control Block
Input/output Queue
Object Request Block
Interrupt Request Block
Prefixed Save Area
Hardware System Area
Channel Subsystem
CPID
UCW
Channel Path Identifier
Unit Control Word
Hardware
HSA
Hardware System Area
Devices
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Device Nr.
Subschannel Nr.
Unit Address
Channel Path Identifier
16 Bit
16 Bit
8 Bit
8 Bit
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Konfigurieren
des Ein-/Ausgabe Subsystems
Das Konfigurieren des Ein-/Ausgabe Subsystems
erfolgt mit Hilfe eines Hardware Configuration
Dialogs (HCD).
HDC Functions
The channel subsystem and the operating system need to
know what hardware resources are available in the system
and how these resources are connected. This information
is called hardware configuration.
The Hardware Configuration Definition (HCD) facility is an
interactive interface that is used to define the hardware
configuration for both the channel subsystem and the
operating system.
The output of HCD is a central repository of configuration
information called the Input/Output Definition File (IODF).
Hardware Configuration Definition
facility
The Hardware Configuration Definition (HCD) facility
runs under TSO. It is a panel-driven facility which
prompts the user.
I/O Devices, Channels
Inhaltlich beschreibt eine I/O-Konfiguration ein
Netzwerk, dessen Endpunkte die Channel Adapter
Karten des Systems und die I/O-Devices darstellen.
Host Channel Path IDs (CPID) werden über
Steuereinheiten (CU) mit Device-Nummern
verbunden.
Die Device-Nummer ist eine vierstellige (16 Bit)
Hexadezimalzahl.
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I/O Definition
Ein z/OS Betriebssystem benötigt eine I/O Definition, um
externe Geräte ansprechen zu können. Diese I/O Definition
ist in der I/O Definition File (IODF) gespeichert.
Die Informationen in dieser Datei müssen zum Zeitpunkt
des IPL dem Betriebssystem bekannt gegeben werden.
Die I/O Definition wird über das z/OS
Konfigurationsprogramm HCD (Hardware Configuration
Dialog) erstellt. Dabei werden zwei unterschiedliche
Konfigurationsdateien erstellt. Die zweite Lage hat
historische Gründe. Sie entstand um die Migration von
älteren auf neuere Systeme zu erleichtern.
 IOCP (I/O Configuration Program) für die Hardware
erstellt IOCDS Datei (Input/Output Configuration Data
Set)
 IODF (I/O Definition File) wird vom Betriebssystem
benutzt.
IOCP wird während des IML (Initial Microprogram Load)
benötigt, damit der Microcode die externen Geräte
ansprechen kann.
Im Wesentlichen werden aus dem IOCP die Subchannel
und aus dem IODF die UCBs generiert.
HDC
IOCP
IOCDS
IODF
gespeichert in der HSA
Channel
Subsystem
z/OS
Kernel
System Initialisierung
The Hardware Configuration Definition (HCD) facility is used at
system installation time to generate a central repository of
configuration information called the Input/Output Definition File
(IODF).
The Input/Output Configuration Program (IOCP) is used to build the
I/O hardware configuration used by the channel subsystem. The
HCD facility uses the IODF to generate input for IOCP. The output of
the IOCP is the Input/Output Configuration Data Set (IOCDS).
The IODF is also used at Initial Program Load (IPL) time to build the
I/O configuration for the z/OS and OS/390 software.
Operating System
I/O Configuration Information
Bei Power-On-Reset wird die IOCDS-Information in
die Hardware System Area (HSA) geladen. Einzelne
Devices werden durch Unit Control Words (UCW)
repräsentiert.
The HSA is addressable only by hardware.
When an Initial Program Load (IPL) is performed for
the z/OS (or OS/390) system, the IODF that defines
the configuration to the system is selected and
used. The Hardware Management Console (HMC)
Load Profile identifies the system residence
(SYSRES) volume and specifies the load parameter.
The load parameter identifies the device number of
the IODF volume.
Die IPL-Daten leitet z/OS aus dem durch den
Loadparameter angesprochenen LOADxx-Member
ab. Die IODF-Zeile dieses LOADxx-Members benennt
den High Level Qualifier und den Suffix der
Datenkomponente eines IODF.
z/OS
When an Initial Program Load (IPL) is performed for
the z/OS or OS/390 system, the IODF that defines the
configuration to the system is used to create the I/O
hardware configuration in the z/OS or OS/390
system area of storage. The eligible device table is
also created at IPL time.
Dynamic Reconfiguration Management
Dynamic reconfiguration support allows changes to be made to the
configration and system defintions without stopping the system.
Dynamic Reconfiguration Management using HCD allows an
installation to define the new I/O interactively and placing the
definitions in the new IODF. Once the I/O is defined it may be
selected using either the HCD panels (HCD ACTIVATE option) or the
ACTIVATE system command.
The activation process updates the z/OS or OS/390 control blocks,
the hardware information in the HSA and also writes the information
to the IOCDS if requested.