Channel subsystem overview
This chapter describes the channel subsystem (CSS), which handles all the system input/output (I/O) operations for IBM Z platforms. The role of the CSS is to control communication between internal or external channels and control units and devices.
This chapter includes the following sections:
2.1 CSS description
CSS enables communication from system memory to peripherals by using channel connections. The channels in the CSS allow transfer of data between memory and I/O devices or other servers under the control of a channel program. The CSS allows channel I/O operations to continue independently of other operations in the system, which allows other functions to resume after an I/O operation is initiated. The CSS also provides internal channels for communication between logical partitions in a physical system.
2.1.1 CSS elements
CSS includes the elements that are described in this subsection.
Channel path
A channel path is a single interface between a system and one or more control units. Commands and data are sent across a channel path to process I/O requests. A CSS can have up to 256 channel paths.
Subchannels
A subchannel provides the logical representation of a device to the program and contains the information that is required to sustain a single I/O operation. One subchannel is assigned per each device that is defined to the logical partition. Subchannel set availability per platform is shown in the following list:
•Four subchannel sets are available on IBM z14 and IBM z13 systems.
•Three subchannel sets are available on IBM z14 ZR1, IBM z13s and IBM zEnterprise EC12 (zEC12).
•Two subchannel sets are available on IBM zEnterprise BC12 (zBC12).
Channel path identifier
The channel subsystem communicates with I/O devices through channel paths between the channel subsystem and control units. Each system channel path is assigned a channel path identifier (CHPID) value that uniquely identifies that path. CSS supports a total of 256 CHPIDs.
On IBM Z, a CHPID number is assigned to a physical location (slot or port) by the user through either the HCD or the IOCP.
Control units
A control unit provides the logical capabilities that are necessary to operate and control an I/O device. It adapts the characteristics of each device so that it can respond to the standard form of control that is provided by the CSS. A control unit can be housed separately, or it can be physically and logically integrated with the I/O device, the channel subsystem, or in the system itself.
I/O devices
An I/O device provides external storage, or a means of communication between data processing systems, or a means of communication between a system and its environment. In the simplest case, an I/O device is attached to one control unit and is accessible through one channel path.
2.1.2 Multiple CSS concept
The IBM Z design offers considerable processing power, memory size, and I/O connectivity. The CSS concept has been scaled up to support the larger I/O capability. IBM Z implements the multiple CSS concept, which provides relief for the number of supported logical partitions, channels, and devices that are available to the system.
Each CSS can have up to 256 channels and can be configured to a maximum of 15 logical partitions1. Table 2-1 lists the maximum number of CSSes and logical partitions that are supported by Z platforms. CSSes are numbered 0 - 5, with the numbers referred to as CSS image IDs.
Table 2-1 Maximum number of CSSes and logical partitions that are supported by IBM Z
Systems
Maximum number of CSSes
Maximum number of logical partitions
z14
6
85
z14 ZR1
3
40
z13
6
85
z13s
3
40
zEC12
4
60
zBC12
2
30
2.1.3 Multiple CSS structure
The structure of multiple CSSes provides channel connectivity to the defined logical partitions in a manner that is apparent to subsystems and application programs. Z platforms enable you to define more than 256 CHPIDs in the system through the multiple CSSes. As previously noted, the CSS defines CHPIDs, control units, subchannels, and so on. This feature enables you to define a balanced configuration for the processor and I/O capabilities.
For easier management, consider using the Hardware Configuration Definitions (HCD) tool to build and control the IBM Z input/output configuration definitions. HCD support for multiple channel subsystems is available with z/VM and z/OS. HCD provides the capability to make dynamic I/O configuration changes.
Logical partitions cannot be added until at least one CSS is defined. Logical partitions are defined for a CSS, not for a system. A logical partition is associated with only one CSS. CHPID numbers are unique within a CSS, but the same CHPID number can be reused within all CSSes.
All channel subsystems are defined within a single I/O configuration data set (IOCDS). The IOCDS is loaded into the hardware system area (HSA) and initialized during power-on reset.
On the Z platform, the HSA has a fixed size, which is not included in the purchased memory. Table 2-2 lists the HSA sizes.
Table 2-2 HSA size
 
z14
z14 ZR1
z13
z13s
zEC12
zBC12
HSA size
192 GB
64 GB
96 GB
40 GB
32 GB
16 GB
Figure 2-1 shows a logical view of these relationships. Each CSS supports up to 15 logical partitions2.
Figure 2-1 Logical view of CSSes, IOCDS, and HSA
2.1.4 Multiple image facility
The multiple image facility (MIF) system function enables resource sharing across logical partitions in a single CSS or across multiple CSSes. Sharing a channel across logical partitions in different CSSes is called spanning. See 2.1.8, “Channel spanning” on page 24 for more information.
With multiple CSSes, the IOCDS logical partition MIF image ID is not unique. Therefore, the logical partition identifier value provides a unique value for each logical partition in the same system.
Logical partition identifier
The logical partition identifier is a number in the following ranges:
•00 to 55 (hex) for the z14 and the z13
•00 to 3F (hex) for the zEC12
•00 to 28 (hex) for z14 ZR1 and z13s
•00 to 1F (hex) for the zBC12.
It is assigned in the image profile through the Support Element (SE) or the Hardware Management Console (HMC), and it is unique across the system. It is also referred to as the user logical partition ID (or user LPAR ID).
Logical partition name
The logical partition name is defined through the HCD or IOCP and is the name in the RESOURCE statement in IOCP. The logical partition names must be unique across all CSSes.
MIF ID
The MIF ID identifier is defined through HCD or IOCP and is the number that is defined in the RESOURCE statement in IOCP as follows:
•The MIF ID is in the range of 1 to F for the zEC12 and zBC12 (all CSSes).
•For z14 and z13, the MIF ID is in the range of 1 to F for CSSes 1 - 5, and from 1 to A for the sixth CSS.
•For z14 ZR1 and z13s, the MIF ID ranges from 1 to F for CSSes 1 and 2, and from 1 to A for the third CSS.
The MIF is unique within a CSS. It is not unique across multiple CSSes because multiple CSSes can specify the same MIF ID, also known as the image ID.
You must establish a numbering convention for the logical partition (LPAR) identifiers. As shown in Figure 2-2, use the CSS number concatenated to the MIF image ID, which means that logical partition ID 3A is in CSS 3 with MIF ID A. This number fits within the allowed range of logical partition IDs and conveys information that is useful to system administrators and operators.
Figure 2-2 Logical partition and MIF definitions
Dynamic addition or deletion of a logical partition name
Because the amount of memory reserved for the HSA is a predefined fixed value, all possible CSSes and LPARs are reserved automatically. They can be added or deleted dynamically by using HCD activations to first add the partition and then, through a subsequent HCD activation, to define and add the connectivity resources to that partition.
2.1.5 Physical channel ID
A physical channel ID (PCHID) reflects the physical location of a channel-type interface. A PCHID number is based on the PCIe I/O drawer, I/O drawer, or I/O cage location, the channel feature slot number, and the port number of the channel feature. A CHPID does not directly correspond to a hardware channel port, but is assigned to a PCHID in HCD or IOCP.
CHPIDs are not preassigned on Z platforms. You must assign the CHPID numbers by using the CHPID Mapping Tool or directly by using HCD/IOCP. Assigning CHPIDs means that the CHPID number is associated with a physical channel port location (PCHID) or the adapter ID (AID) and a CSS. The CHPID number range is from 00 to FF and must be unique in a CSS. Any CHPID that is not connected to a PCHID fails validation when an attempt is made to build a production IODF or an IOCDS.
Figure 2-3 shows the front view of the PCIe I/O drawer 4 (bottom of the frame), including I/O features in slots 01 - 04, and the PCHID numbers.
Figure 2-3 PCHID example: Front of PCIe I/O drawer
Example 2-1 shows a portion of a sample PCHID REPORT for an IBM z13 system.
Example 2-1 PCHID REPORT for a z13
CHPIDSTART
12345678 PCHID REPORT Oct 28,2014
Machine: 2964-NE1 SNXXXXXXX
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Source Cage Slot F/C PCHID/Ports or AID Comment
A27/LG07 A27A LG07 0170 AID=00
A15/LG04 A15A LG04 0172 AID=30
A19/LG15/J01 Z22B 03 0414 108/D1D2
A19/LG15/J01 Z22B 04 0418 10C/D1 10D/D2
A19/LG03/J01 Z08B 20 0411 240/D1D2 RG2
A27/LG14/J01 Z01B 03 0420 288 RG1
A23/LG14/J01 Z01B 19 0411 2BC/D1D2 RG1
A15/LG05/J01 A32B 38 0420 37C RG2
 
Legend:
Source Book Slot/Fanout Slot/Jack
A15A Processor Drawer 1 in A frame
A19A Processor Drawer 2 in A frame
A23A Processor Drawer 3 in A frame
A27A Processor Drawer 4 in A frame
Z22B PCIe Drawer 1 in Z frame
Z15B PCIe Drawer 2 in Z frame
Z08B PCIe Drawer 3 in Z frame
Z01B PCIe Drawer 4 in Z frame
A32B PCIe Drawer 5 in A frame
RG1 Resource Group One
RG2 Resource Group Two
0170 HCA3 0 LR PSIFB 1x 4 Links
0172 Integrated Coupling Adapter (ICA SR) 2 Links
0411 10GbE RoCE Express
0414 OSA Express5S GbE SX 2 Ports
0418 16 Gbps FICON/FCP LX 2 Ports
0420 zEDC Express
The following list explains the content of the sample PCHID REPORT:
•Feature code 0170 (HCA3-O LR [1x IFB]) is installed in CPC drawer 4 (location A27A, slot LG07) and has AID 00 assigned.
•Feature code 0172 (Integrated Coupling Adapter [ICA SR]) is installed in CPC drawer 1 (location A15A, slot LG04) and has AID 30 assigned.
•Feature code 0414 (OSA-Express5S GbE short wavelength [SX]) is installed in PCIe I/O drawer 2 (location Z22B, slot 03) and has PCHID 108 assigned. PCHID 108 is shared by ports D0 and D1.
•Feature code 0418 (FICON Express16S long wavelength [LX] 10 km [6.2 miles]) is installed in PCIe I/O drawer 2 (location Z22B, slot 04) and has PCHIDs 10C and 10D assigned.
•Feature code 0411 (10GbE RoCE Express) is installed in PCIe I/O drawer 3 (location Z08B, slot 20) and has PCHID 240 assigned. PCHID 240 is shared by ports D0 and D1.
A resource group (RG) parameter is shown in the PCHID REPORT for native PCIe features. There is a balanced plugging of native PCIe features between two resource groups (RG1 and RG2).
You can get a PCHID report from the IBM account team when ordering.
2.1.6 Adapter ID
The adapter ID (AID) number assigns a CHPID to a port by using HCD/IOCP for IBM Parallel Sysplex cluster technology.
On the Z platform, the AID is bound to the serial number of the fanout. If the fanout is moved, the AID moves with it. No IOCDS update is required if adapters are moved to a new physical location.
Table 2-3 lists the assigned AID numbers for a zEC12 new build.
Table 2-3 Fanout AID numbers for zEC12
Fanout location
Book
 
Fourth
First
Third
Second
D1
00
08
10
18
D2
01
09
11
19
D3
N/A
N/A
N/A
N/A
D4
N/A
N/A
N/A
N/A
D5
02
0A
12
1A
D6
03
0B
13
1B
D7
04
0C
14
1C
D8
05
0D
15
1D
D9
06
0E
16
1E
DA
07
0F
17
1F
Table 2-4 lists the assigned AID numbers for a zBC12 new build.
Table 2-4 AID number assignment for zBC12
Fanout location
Processor drawer
 
Processor drawer 0
Processor drawer 1
D1
08
00
D2
09
01
D7
0A
02
D8
0B
03
Table 2-5 lists the assigned AID numbers for a z13 new build.
Table 2-5 Fanout AID numbers for z13
Drawer1 (DX)2
Location
Fanout slot
AIDs
First (D3)
A15A
LG02-LG06 (PCIe)
2E-32
LG07-LG10 (IFB)
0C-0F
LG11-LG15 (PCIe)
33-37
Second (D2)
A19A
LG02-LG06 (PCIe)
24-28
LG07-LG10 (IFB)
08-0B
LG11-LG15 (PCIe)
29-2D
Third (D1)
A23A
LG02-LG06 (PCIe)
1A-1E
LG07-LG10 (IFB)
04-07
LG11-LG15 (PCIe)
1F-23
Fourth (D0)
A27A
LG02-LG06 (PCIe)
10-14
LG07-LG10 (IFB)
00-03
LG11-LG15 (PCIe)
15-19
1 Indicates the z13 physical CPC drawer installation order.
2 The designation between the parenthesis indicates the logical CPC drawer number.
AIDs are included in the PCHID report that IBM provides for new build systems and upgrades. Example 2-2 shows an AID in a PCHID report.
Example 2-2 AID assignment in z13 PCHID report
CHPIDSTART
12345678 PCHID REPORT Oct 31,2014
Machine: 2964-NE1 SNXXXXXXX
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Source Cage Slot F/C PCHID/Ports or AID Comment
A15/LG02         A15A LG02  0172   AID=2E
A19/LG11         A19A LG11  0172 AID=29
 
Table 2-6 lists the AID assignment for each fanout slot relative to the drawer location on a z13s new build system.
Table 2-6 AID number assignment for IBM z13s
Drawer
Location
Fanout slot
AIDs
First
A21A
LG03-LG06 (PCIe)1
1B-1E
LG07-LG10 (IFB)a
04-07
LG11-LG14 (PCIe)
1F-22
Second
A25A
LG03-LG06 (PCIe)
11-14
LG07-LG10 (IFB)
00-03
LG11-LG14 (PCIe)
15-18
1 For model N10, only the first drawer’s LG09-LG10 supported for IFB, and LG11-LG14 supported for PCIe
Table 2-7 lists the assigned AID numbers for a z14 new build system.
Table 2-7 Fanout AID numbers for z14
Drawer1 (DX)2
Location
Fanout slot
AIDs
First (D3)
A15A
LG03-LG12 (PCIe)
2E-37
LG13-LG16 (IFB)
0C-0F
Second (D2)
A19A
LG03-LG12 (PCIe)
24-2D
LG13-LG16 (IFB)
08-0B
Third (D1)
A23A
LG03-LG12 (PCIe)
1A-23
LG13-LG16 (IFB)
04-07
Fourth (D0)
A27A
LG03-LG12 (PCIe)
10-19
LG13-LG16 (IFB)
00-03
1 Indicates the z14 physical CPC drawer installation order.
2 The designation between the parenthesis indicates the logical CPC drawer number.
Table 2-8 lists the assigned AID numbers for a z14 ZR1 new build system.
Table 2-8 AID number assignment for z14 ZR1
Fanout location
CPC Drawer Location
AIDs
LG01 - LG04
A09B
10 - 13
LG07 - LG10
14 - 17
2.1.7 Multiple CSS construct example
Each CSS has three logical partitions with their associated MIF image identifiers. In each CSS, the CHPIDs are shared across all logical partitions. The CHPIDs are assigned to their designated PCHIDs. Figure 2-4 shows two CSSes defined as CSS0 and CSS1.
Figure 2-4 Multiple CSS construct
The CHPIDs are mapped to their designated PCHIDs by using the Channel Mapping Tool or manually by using HCD or IOCP.
The output of the Channel Mapping Tool is used as input to HCD or the IOCP to establish the CHPID-to-PCHID assignments. See 2.2, “I/O configuration management” on page 28 for more information about the Channel Mapping Tool.
2.1.8 Channel spanning
Channel spanning extends the MIF concept of sharing channels across logical partitions to sharing channels across channel subsystems and logical partitions.
Spanning is the ability for the channel to be configured to multiple channel subsystems. When so defined, the channels can be transparently shared by any or all of the configured logical partitions, regardless of the channel subsystem to which the logical partition is configured.
A channel is considered a spanned channel if the same CHPID number in different CSSes is assigned to the same PCHID in the IOCP or is defined as spanned in HCD. The same applies to internal channels such as IBM HiperSockets3 technology, but there is no PCHID association. Internal channels are defined with the same CHPID number in multiple CSSes.
CHPIDs that span CSSes reduce the total number of channels that are available on IBM Z. The total is reduced because no CSS can have more than 256 CHPIDs. For a zBC12 that supports two CSSes, a total of 512 CHPIDs are supported. For a zEC12 with four CSSes, a total of 1024 CHPIDs are supported. For a z14 and z13 with six CSSes, a total of 1536 CHPIDs are supported. For a z14 ZR1 and z13s with three CSSes, a total of 768 CHPIDs are supported.
If all CHPIDs are spanned across the two, four, or six CSSes depending on the server, only 256 channels can be supported. Table 2-9 shows which channel types can be defined as shared or spanned channels.
Table 2-9 Spanned and shared channel
Channel type
CHPID definition
Shared channels
Spanned channels
FICON Express4
External
FC, FCP
Yes
Yes
FICON Express8
External
FC, FCP
Yes
Yes
FICON Express8S
External
FC, FCP
Yes
Yes
FICON Express16S
External
FC, FCP
Yes
Yes
FICON Express16S+
External
FC, FCP
Yes
Yes
zHyperLink Express
External
N/A
Yes
Yes
OSA-Express31
External
OSD, OSE, OSC, OSN, OSX, OSM
Yes
Yes
OSA-Express4Sa
External
OSD, OSE, OSC, OSN, OSX, OSM
Yes
Yes
OSA-Express5Sa
External
OSD, OSE, OSC, OSN, OSX, OSM
Yes
Yes
OSA-Express6Sa
External
OSD, OSE, OSC, OSX, OSM
Yes
Yes
OSA-Express7S2
External
OSD, OSX
Yes
Yes
ICA SR
External
CS5
Yes
Yes
CE LR
External
CL5
Yes
Yes
IFB
External
CIB
Yes
Yes
ISC-3
External
CFP
Yes
Yes
IC
Internal
ICP
Yes
Yes
HiperSockets3
Internal
IQD
Yes
Yes
1 Not every type of CHPID is supported by the different OSA-Express features. For more information, see Chapter 5, “Open Systems Adapter-Express” on page 71.
2 OSA-Express7S 25GbE SR
3 The CHPID statement of HiperSocket devices requires the keyword VCHID. VCHID specifies the virtual channel identification number associated with the channel path. The valid range is 7C0 - 7FF. VCHID is not valid on IBM Z products before z13.
In Figure 2-5, CHPID 04 is spanned across CSS 0 and CSS 1. Because it is not an external channel link, no PCHID is assigned. CHPID 06 is a spanned external channel and has PCHID 120 assigned.
Figure 2-5 Two channel subsystems with spanned channels (internal and external)
2.1.9 Multiple subchannel sets
Do not confuse the multiple subchannel sets (MSS) functions with multiple channel subsystems. In most cases, a subchannel represents an addressable device. For example, a disk control unit with 30 drives uses 30 subchannels. An addressable device is associated with a device number.
Subchannel numbers, including their implied path information to devices, are limited to four hexadecimal digits by hardware and software architectures. Four hexadecimal digits provide 64 thousand addresses, which are known as a set. IBM reserved 256 subchannels, leaving 63.75 thousand subchannels for general use with IBM Z platforms. Parallel access volumes (PAVs) make this limitation of subchannels a challenge for larger installations. A single-disk drive (with PAVs) often uses at least four subchannels4.
It was difficult to remove this constraint because the use of four hexadecimal digits for subchannels and device numbers that correspond to subchannels is specified in several places. Simply expanding the field would break too many programs.
The solution allows sets of subchannels (addresses) with a current implementation of four sets with z14 and z13, and three sets with z14 ZR1, z13s, and zEC12. Each set provides 64 thousand addresses minus one. Subchannel set 0, the first set, reserves 256 subchannels for use by IBM. Subchannel set 1 provides a full range of 64 thousand minus one subchannel on the Z platform. Subchannel set 2 provides another full range of 64 thousand, minus one subchannels on z14, z14 ZR1, z13, z13s, and zEC12 systems only. Subchannel set 3, the fourth set, provides another full range of 64 thousand, minus one subchannel on z14 and z13.
The first subchannel set (SS0) allows definitions of any type of device that is supported, for example, bases, aliases, secondaries, and devices, other than disks that do not implement the concept of associated aliases or secondaries.
The second, third, and fourth subchannel sets (SS1, SS2, and SS3) are designated for use for disk alias devices, both primary and secondary devices, and for IBM Metro Mirror secondary devices only.
There is no required correspondence between addresses in the three sets. For example, it is possible to have device number 8000 in subchannel set 0 and device number 8000 in subchannel sets 1 or 2, and they can refer to different devices. Likewise, device number 1234, subchannel set 0, and device number 4321, subchannel set 1, might be the base and an alias for the same device.
There is no required correspondence between the device numbers that are used in the four subchannel sets. Each channel subsystem can have multiple subchannel sets, as shown in Figure 2-6.
Figure 2-6 Multiple CSSes and multiple subchannel sets5
The appropriate subchannel set number must be included in IOCP definitions or in the HCD definitions that produce the IOCDS. The subchannel set number defaults to zero, and IOCP changes are needed only when using subchannel sets 1, 2, or 3.
IPL from an alternative subchannel set
z14 and z13 support IPL from subchannel sets 0, 1, 2, and 3. z14 ZR1, z13s and zEC12 support IPL from subchannel sets 0, 1, and 2, and zBC12 supports IPL from subchannel sets 0 and 1. Devices that are used early during IPL processing can now be accessed by using subchannel set 1, subchannel set 2, or subchannel set 3.
This feature allows the users of Metro Mirror (Peer-to-Peer Remote Copy, or PPRC) secondary devices. These devices are defined by using the same device number and a new device type in an alternative subchannel set to be used for IPL, IODF, and stand-alone memory dump volumes when needed.
IPL from an alternative subchannel set is supported on the Z platform. It is supported by z/OS V2.2, V2.1, and V1.13 and V1.126 with program temporary fixes (PTFs). It applies to the IBM Fibre Channel connection (FICON) and High Performance FICON for IBM Z® (zHPF) protocols.
2.1.10 Summary
Table 2-10 lists the maximum number of CSS elements that are supported per Z platform.
Table 2-10 CSS elements
 
zBC12
zEC12
z13s
z13
z14 ZR1
z14
CSSes
2 per system
4 per system
3 per system
6 per system
3 per system
6 per system
Partitions
15 per CSS, up to 30 per system
15 per CSS, up to 60 per system
15 for the first two CSSes and 10 for the third, up to 40 per system
15 for the first 5 CSSes and 10 for the sixth, up to 85 per system
15 for the first two CSSes and 10 for the third, up to 40 per system
15 for the first 5 CSSes and 10 for the sixth, up to 85 per system
CHPIDs
256 per CSS, up to 512 per system
256 per CSS, up to 1024 per system
256 per CSS,
up to 768 per system
256 per CSS, up to 1536 per system
256 per CSS,
up to 768 per system
256 per CSS, up to 1536 per system
Devices
63,750 on SS0;
64,000 - 1 on SS1
63,750 on SS0;
64,000 - 1 on SS1 and SS2
63,750 on SS0;
64,000 - 1 on SS1 and SS2
63,750 on SS0;
64,000 - 1 on SS1, SS2, and SS3
63,750 on SS0;
64,000 - 1 on SS1 and SS2
63,750 on SS0;
64,000 - 1 on SS1, SS2, and SS3
2.2 I/O configuration management
CSS controls communication between a configured channel, the control unit, and the device. The IOCDS defines the channels, control units, and devices to the designated logical partitions within the system. This communication is defined by using the IOCP.
The IOCP statements typically are built by using the HCD. An interactive dialog is used to generate the input/output definition file (IODF), start the IOCP program, and then build the production IOCDS. The IOCDS is loaded into the HSA and initialized during power-on reset. In prior Z servers, the HSA storage was allocated based on the size of the IOCDS, partitions, channels, control units, and devices. Additional storage was reserved for dynamic I/O reconfiguration, if enabled.
The HSA has the following fixed sizes:
•On z14, the fixed size is 192 GB.
•On z13, the fixed size is 96 GB.
•On z14 ZR1, the fixed size is 64 GB.
•On z13s, the fixed size is 40 GB.
•On zEC12, the fixed size is 32 GB.
•On zBC12, the fixed size is 16 GB.
With Z platforms, CHPIDs are mapped to PCHIDs or AIDs by using the configuration build process through HCD or IOCP (see 2.1.6, “Adapter ID” on page 21). There is no PCHID association for internal channels (that is, IC links and IBM HiperSockets).
The sections that follow describe tools that are used to maintain and optimize the I/O configuration on Z platforms.
2.2.1 Hardware configuration definition
HCD supplies an interactive dialog to generate the IODF and then the IOCDS. Consider using the HCD to generate the IOCDS, as opposed to writing IOCP statements. The validation checking that HCD does as data is entered helps eliminate errors before the I/O configuration is implemented.
2.2.2 CHPID Mapping Tool
The CHPID Mapping Tool helps with IBM Z requirements. It provides a mechanism to map CHPIDS to PCHIDS and identify the best availability options for installed features and defined configuration.
Consider using the mapping tool for all new builds of IBM Z family or when upgrading from one system to another. You can also use it as part of standard hardware changes (for example, MES) for an existing Z mainframe.
The mapping tool takes input from two sources:
•The Configuration Report file (CFreport) produced by the IBM order tool and provided by the IBM account team, or produced by IBM manufacturing and obtained from IBM Resource Link®
•An IOCP statement file
The mapping tool produces the following outputs:
•Tailored reports
Save all reports for reference. Supply the port report that is sorted by CHPID number and location to the IBM hardware service representative for IBM Z installations.
•An IOCP input file with PCHIDs mapped to CHPIDs
This IOCP input file can then be migrated back into HCD and used to build a production IODF.
The mapping tool does not automatically map CS5 or CIB CHPIDs to AIDs and ports. This process must be done manually, either in HCD, IOCP, or the mapping tool. The mapping tool provides availability intersects for completely defined CIB CHPIDs. For more information on the CHPID Mapping Tool go to:
2.3 I/O configuration planning
I/O configuration planning for IBM Z requires the availability of physical resources, and must comply with the specific rules of the logical definitions. The following physical resources are the minimum that is required for connectivity:
•Platform frame (or rack)
•PCIe+ I/O drawer, PCIe I/O drawer, I/O drawer, or I/O cage, in a frame (or rack)
•I/O slot in a PCIe+ I/O drawer, PCIe I/O drawer, I/O drawer, or I/O cage
•Channel feature in a slot of a PCIe+ I/O drawer, PCIe I/O drawer, I/O drawer, or I/O cage
•Port on a channel feature
For a system configuration, the Z configurator build process includes all physical resources that are required for a particular I/O configuration, based on the supplied channel type and quantity requirements.
The definition phase starts after the physical resources are ordered. The channels must be defined according to the architecture’s rules, the system’s implementation, and the order.
There are also other definition implications that are imposed by the system implementation, such as the maximum number of subchannels in the HSA:
•3832.5 thousand subchannels total (63.75 thousand per partition x 30 partitions + 64 thousand per partition x 30 partitions) for the zBC12
•11,505 thousand subchannels total (63.75 thousand per partition x 60 partitions +
2 x 64 thousand per partition x 60 partitions) for the zEC12
•21,738.75 thousand subchannels total (63.75 thousand per partition x 85 partitions +
3 x 64 thousand per partition x 85 partitions) for the z14 and the z13
•7670 thousand subchannels total (63.75 thousand per partition x 40 partitions + 2 x 64 thousand per partition x 40 partitions) for the z14 ZR1 and z13s
The operational characteristics of a particular channel type, along with the addressing capabilities, can affect configuration complexity, topology, infrastructure, and performance.
2.3.1 I/O configuration rules
The following sections briefly describe the Z configuration rules, which are identified through the architecture and the specific system that are implemented and enforced by using the HCD and IOCP.
All control units and I/O devices that attach to the system must be defined to a CSS. Specify the following items when defining the I/O configuration for the system through HCD/IOCP:
•Logical partitions (logical partition name, CSS ID, and MIF ID, where appropriate)
•Channel paths on the system, their assignment to CSSes, and logical partitions
•FICON Directors (where appropriate)
•Control units that are attached to the channel paths
•I/O devices that are assigned to the control units
 
Cryptographic features: The cryptographic features on IBM Z do not require a CHPID definition and are configured by using the HMC or SE.
Certain definition characteristics that must be considered for the I/O configuration are found in the architecture (z/Architecture). Other definition characteristics are specified only for the system. Table 2-11 lists general IOCP rules for IBM Z.
Table 2-11 IBM Z general IOCP rules
Constant machine attributes
z14, z14 ZR1, z13, z13s, zEC12, and zBC12
Maximum configurable physical control units (PCUs)
 
PCUs per OSD
16
PCUs per OSE, OSC, OSN1
1
PCUs per OSM, OSX
16
PCUs per CFP, ICP
1
PCUs or link addresses per FC
256
PCUs per FCP
1
CUs per IQD
64
Maximum configurable devices
Per CFP, ICP, CIB (12x IFB, or 1x IFB), CS5, CL5
8
CIB (1x IFB)
32
Per CNC
1024
Per CTC
512
Per OSC2
253
Per OSD
1920
Per OSE
254
Per OSM, OSX
1920
Per OSNa
480
Per FCP
480
Per FC
32,0003
For all IQD channel paths
12,000
1 OSN CHPID type NOT supported on z14 or z14 ZR1.
2 A limit of 120 clear sessions and 48 encrypted sessions can be defined at the HMC/SE.
3 zEC12 and zBC12 support 24,000 FC channels.
See IBM Z Input/Output Configuration Program User’s Guide for ICP IOCP, SB10- 7172, for details about CHPID types and channel configuration rules.
2.4 References
The following publications include information that is related to the topics covered in this chapter:
•z/OS Hardware Configuration Definition User’s Guide, SC34-2669
•z/OS Hardware Configuration Definition Planning, GA32-0907
•Hardware Configuration Definition: User’s Guide, SC28-1848
•Hardware Configuration Definition Planning, GC28-1750
•Input/Output Configuration Program User's Guide for ICP IOCP, SB10- 7172
•IBM zEnterprise EC12 Technical Guide, SG24-8049
•IBM zEnterprise BC12 Technical Guide, SG24-8138
•IBM zEnterprise System Technical Introduction, SG24-8050
•IBM z13 and IBM z13s Technical Introduction, SG24-8250
•IBM z13 Technical Guide, SG24-8251
•IBM z13s Technical Guide, SG24-8294
•IBM z14 Technical Introduction, SG24-8450
•IBM z14 Technical Guide, SG24-8451
•IBM z14 ZR1 Technical Introduction, SG24-8550
•IBM z14 ZR1 Technical Guide, SG24-8651
1 The z14 and z13 support 10 logical partitions in the sixth CSS, while z14 ZR1 and z13s support 10 logical partitions in the third CSS.
2 The sixth CSS (CSS5) on z14 and z13 supports 10 LPARs, Same rule applies for third CSS (CSS2) on z14 ZR1 and z13s.
3 The CHPID statement of HiperSocket devices requires the keyword VCHID. VCHID specifies the virtual channel identification number that is associated with the channel path. The valid range is 7C0 - 7FF. VCHID is not valid on IBM Z products before z13.
4 Four subchannel sets are mostly used in conjunction with PAV. They represent base addresses and three alias addresses.
5 The number of subchannels sets in this figure applies to zEC12.
6 z/OS V1.12 is not supported on z14.
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