114 IBM ^ zSeries 990 Technical Guide
In each LCSS, the CHPIDs are shared across all logical partitions. The CHPIDs in each
LCSS can be mapped to their designated PCHIDs using the CHPID Mapping Tool (CMT), or
manually using HCD or IOCP. The output of the CMT is used as input to HCD or the IOCP to
establish the CHPID to PCHID assignments. See 4.2.1, “z990 configuration management” on
page 116 for further details on the CMT.
Figure 4-3 z990 LCSS connectivity
4.1.3 Channel spanning
Channel spanning extends the MIF concept of sharing channels across logical partitions to
sharing channels across logical partitions
and Logical Channel Subsystems.
Spanning is the ability for the channel to be configured to multiple Logical Channel
Subsystems. When defined that way, the channels can be transparently shared by any or all
of the configured logical partitions, regardless of the Logical Channel Subsystem to which the
logical partition is configured.
A channel is considered a spanned channel if the same CHPID number in different LCSSs is
assigned to the same PCHID in IOCP, or is defined as “spanned” in HCD.
In the case of internal channels (for example, IC links and HiperSockets), the same applies,
but there is no PCHID association. They are defined with the same CHPID number in multiple
LCSSs.
CHPIDs that span LCSSs reduce the total number of channels available on the z990. The
total is reduced, since no LCSS can have more than 256 CHPIDs. For a z990 with two
LCSSs, a total of 512 CHPIDs are supported. If all CHPIDs are spanned across the two
LCSSs, then only 256 channels can be supported. For a z990 with four LCSSs, a total of
1024 CHPIDs are supported. If all CHPIDs are spanned across the four LCSSs, then only
256 channels can be supported.
DASD
LCUs
5
LP16
LP2 LP3 LP14
LP15
LP1
235
LCSS 1
31
LCSS 0
81 90 918081 90 9180
151 1E1 1F1141150 1E0 1F0140
LCSS
LPAR name
PCHID
MIF ID
CHPID
DASD
LCUs
Directors
Control Units
and Devices
0201
LPAR ID
1A0B 0C 11 1300
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