IBM z/OS - page 9

Each book can support up to 64 GB of Memory, delivered

on two memory cards, and 12 STIs giving a total of 256 GB

of memory and 48 STIs on the D32 model. The memory is

delivered on 8 GB, 16 GB or 32 GB memory cards which

can be purchased in 8 GB increments. The minimum

memory is 16 GB. The two memory cards associated with

each book must be the same size. Each book has 3 MBAs

and each MBA supports 4 STIs.

All books are interconnected with a super-fast bi-direc-

tional redundant ring structure which allows the system to

be operated and controlled by PR/SM operating in LPAR

mode as a symmetrical, memory coherent, multiproces-

sor. PR/SM provides the ability to conﬁ gure and operate

as many as 30 Logical Partitions which may be assigned

processors, memory and I/O resources from any of the

available books. The z990 supports LPAR mode only (i.e.

basic mode is no longer supported).

The MultiChip Module is the technology cornerstone for

ﬂ exible PU deployment in the z990 models. For most

models, the ability of the MCM to have inactive PUs allows

such features as Capacity Upgrade on Demand (CUoD),

Customer Initiated Upgrades (CIU), and the ability to add

CPs, ICFs, IFLs, and zAAPs dynamically providing nondis-

ruptive upgrade of processing capability. Also, the ability

to add CPs lets a z990 with spare PU capacity become a

backup for other systems in the enterprise; expanding the

z990 system to meet an emergency outage situation. This

is called Capacity BackUp (CBU). The greater capacity of

the z990 offers customers even more ﬂ exibility for using

this feature to backup critical systems in their enterprise.

In order to support the highly scalable multi-book system

design the I/O SubSystem has been enhanced by intro-

ducing a new Logical Channel SubSystem (LCSS) which

provides the capability to install up to 1024 CHPIDs across

three I/O cages (256 per operating system image). I/O

improvements in the Parallel Sysplex Coupling Link archi-

tecture and technology support faster and more efﬁ cient

transmission between the Coupling Facility and production

systems. HiperSockets™ provides high-speed capability to

communicate among virtual servers and Logical Partitions;

this is based on high-speed TCP/IP memory speed trans-

fers and provides value in allowing applications running

in one partition to communicate with applications running

in another without dependency on an external network.

Industry standard and openness are design objectives for

I/O in z990. The improved I/O subsystem is delivering new

horizons in I/O capability and has eliminated the 256 limit

to I/O attachments for a mainframe.