IBM 990 - Manual (Page 123)

Chapter 4. Channel Subsystem 111
It is important to note that an IBM 2084 is one processor with logical extensions. All Channel
Subsystem Images (CSS Image or LCSS) are defined within a single IOCDS. The IOCDS is
loaded and initialized into the Hardware System Area at Power-on Reset.
There is no HSA expansion support for dynamic I/O on the z990 Support Element. The HSA
allocation is controlled by the “maximum number of devices” field on the HCD Channel
Subsystem List panel. This value can only be changed by a Power-on Reset. Figure 4-1
shows a logical view of the relationships. It must be noted that each LCSS supports up to 15
logical partitions, but system wide, a total of up to 30 logical partitions are supported.
Figure 4-1 Logical view of IBM 2084 models, LCSSs, IOCDS and HSA
1
The channel definitions of an LCSS are not bound to a single book. An LCSS may define
resources that are physically connected to all STIs of all books in any multi-book IBM 2084
model.
Multiple Image Facility (MIF)
Multiple Image Facility (MIF) enables resource sharing across logical partitions within a single
LCSS or across the LCSSs. When a channel resource is shared across logical partitions in
multiple LCSS, this is known as “spanning”; refer to 4.1.3, “Channel spanning” on page 114
for more information about spanning.
With the introduction of multiple LCSSs, the IOCDS logical partition MIF Image ID is no longer
unique within the z990 server. Therefore, the logical partition identifier value has been
changed to provide a unique value for each logical partition within the same z990 server. The
following terminology applies:
Logical partition number
The logical partition number cannot be specified by the user; actually, it is not even visible to
the user. On the z990, it is assigned at Power-on Reset by PR/SM and is based on the total
1
Although each LCSS supports up to 15 logical partitions, it should be noted that, system wide, up to 30 logical partitions are
supported.
Note: HSA is always allocated in the physical memory of Book 0.
1-8 PUs 0-8 PUs 0-8 PUs 0-8 PUs
Driver
B16
C24
D32
16 - 64 GB 0 - 64 GB 0 - 64 GB 0 - 64 GB
A08
Logical Partitions
Single Driver/LIC (CEC-wide)
Up to 4 books per CEC
Active Processing Units (min 1, max 32)
Memory (min 16 GB, max 256 GB)
Self-Timed Interconnect cables
Single HSA with one active IOCDS that
provides a single system image for I/O
Up to 4 Logical Channel Subsystems
I/O Cage with features
HSA
1-12 STIs 0-12 STIs 0-12 STIs 0-12 STIs
Physical Channels (PCHIDs)
LCSS 0
up to 256
CHPIDs
Up to 15 Logical Partitions per LCSS
Up to 30 Logical Partitions per CEC
LCSS 1
up to 256
CHPIDs
LCSS 2
up to 256
CHPIDs
LCSS 3
up to 256
CHPIDs
IOCDS