IBM 990 - Manual (Page 84)

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zSeries 990 Technical Guide
Dynamic I/O reconfiguration
Dynamic I/O reconfiguration enhances system availability by supporting the dynamic
addition, removal, or modification of channel paths, control units, I/O devices, and I/O
configuration definitions to both hardware and software (if it has this support), without
requiring a planned outage.
ESCON port sparing and upgrading
The ESCON 16-port I/O card includes one unused port dedicated for sparing in the event
of a port failure on that card. Other unused ports are available for growth of ESCON
channels without requiring new hardware, enabling concurrent upgrades via Licensed
Internal Code.
For detailed information about the I/O system structure, see Chapter 3, “I/O system structure”
on page 73.
2.2.13 Channel Subsystem
The representation of all connections and devices is called the Channel Subsystem. The
z990 introduces the concept of Multiple Logical Channel Subsystems. Up to two Logical
Channel Subsystems (LCSSs) can be defined in the IOCDS, and this allows for the definition
of up to 512 channels. One IOCDS describes the complete I/O configuration and one HSA
after Power-On Reset (POR). The HSA is always located in the physical memory of Book 0.
Logical Channel Subsystem (LCSS)
A Logical Channel Subsystem (LCSS) is a logical collection of up to 256 CHPIDs that are
mapped to physical channels with the assistance of HCD, the Channel Mapping Tool (CMT),
and IOCP. Physical channels are represented in the system by Physical Channel IDs
(PCHIDs). The z990 supports up to two LCSSs (512 CHPIDs), but the Multiple CSS
architecture allows for more LCSSs.
Physical Channel ID (PCHID)
PCHIDs identify the physical ports on cards located in I/O cages and follow the numbering
scheme listed in Table 2-11.
Table 2-11 PCHID locations
Introduction of PCHIDs means that CHPIDs are no longer pre-assigned. It is the responsibility
of the user to assign the CHPID numbers through the use of HCD/IOCP, and the CHPID
mapping tool. Assigning a CHPID means that the CHPID number is associated with a
physical channel port location (PCHID) and an LCSS (LCSS0 or LCSS1). CHPID numbers
still range from 00 to FF and must be unique within an LCSS.
For more detailed information about the Logical Channel Subsystem structure, see 4.1.1,
“Logical Channel Subsystem structure” on page 110.
Cage Front PCHID ## Rear PCHID ##
I/O Cage 1 100 - 1FF 200 - 2FF
I/O Cage 2 300 - 3FF 400 - 4FF
I/O Cage 3 500 - 5FF 600 - 6FF
CEC Cage 000 - 0FF reserved for ICB-4