52 IBM eServer zSeries 900 Technical Guide
Hiperspaces on z/Architecture mode
Hiperspace services have been re-implemented to use central storage rather than expanded
storage. All of the Hiperspace APIs, as well as the Move Page (MVPG) instruction, continue
to operate in a compatible manner. There is no need to change products that use
Hardware System Area
The Hardware System Area (HSA) is a non-addressable storage area that contains the CPC
Licensed Internal Code and configuration-dependent control blocks. The HSA size varies
according to:
򐂰 Power-On-Reset mode of the CPC.
򐂰 Number of installed processors.
򐂰 Size and complexity of the system I/O configuration.
򐂰 The expansion percentage used for dynamic I/O configuration.
For planning purposes, you can assume the following HSA maximum sizes:
Basic mode: 144 MB.
LPAR mode and memory <= 32 GB: 288 MB.
LPAR mode and memory > 32 GB: 384 MB.
The z900s HSA can have up to 63K subchannels per logical partition and up to 512K
subchannels in total.
2.5.2 Storage operations
In the z900 servers, memory can be assigned as a combination of central storage and
expanded storage, supporting up to 15 logical partitions in LPAR mode.
Before one can activate a logical partition, central storage (and optional expanded storage)
must be defined to the logical partition. In LPAR mode, all installed storage can be configured
as central storage. Each individual logical partition can be defined to a maximum of 2 GB (in
ESA/390 architecture mode) or the current maximum 64 GB (in z/Architecture mode) of
central storage.
In LPAR mode, central storage can be dynamically assigned to expanded storage and back to
central storage as needed, without a Power-On-Reset (POR). See LPAR single storage pool
on page 51.
cannot be shared between system images. When a logical partition is activated, the
storage resources are allocated in contiguous blocks. You can dynamically reallocate storage
resources for z/Architecture and ESA/390 Architecture mode logical partitions running
operating systems that support Dynamic Storage Reconfiguration (DSR). See LPAR
Dynamic Storage Reconfiguration on page 56.
Operating systems running under z/VM can exploit the z/VM capability of implementing virtual
memory to guest virtual machines. The z/VM dedicated
real storage can be shared
between guest operating systems memories.
Figure 2-16 shows the z900 modes and memory diagram, which summarizes all image
modes, with their processor types and the Central Storage (CS) and Expanded Storage (ES)
definitions allowed for each mode.
Chapter 2. zSeries 900 system structure 53
Figure 2-16 Modes and memory diagram
Table 2-8 shows the z900 storage
allocation and usage possibilities, which depend upon the
image and architecture modes.
Table 2-8 Storage definition and usage possibilities
Remember that either a z/Architecture mode or an ESA/390 architecture mode operating
system can run in an ESA/390 mode on a z900. Any ESA/390 image, in Basic mode or in
LPAR mode, can be configured with more than 2 GB of central storage
and can have
expanded storage. These options allow you to configure more storage resources than the
operating system is capable of addressing.
ESA/390 mode
In ESA/390 mode, storage addressing can be 31 or 64 bits, depending on the operating
system architecture
and the operating system configuration.
Image mode Architecture mode
Maximum central storage Expanded storage
Architecture z900
system usage
ESA/390 z/Architecture (64-bit) 16 EB 64 GB yes only by z/VM
ESA/390 (31-bit) 2 GB 64 GB yes yes
ESA/390 TPF ESA/390 (31-bit) 2 GB 64 GB yes yes
Coupling Facility CFCC (64-bit) 16 EB 64 GB no no
Linux Only z/Architecture (64-bit) 16 EB 64 GB yes
only by z/VM
ESA/390 (31-bit) 2 GB 64 GB yes yes
z900 CPC
ESA/390 Mode
ESA/390 TPF Mode
Coupling Facility Mode
Linux Only Mode
Definable Central Storage (CS)
and Expanded Storage (ES)
CS < = 64 GB
ES = Yes
CS < = 64 GB
ES = Yes
CS < = 64 GB
ES = No
CS < = 64 GB
ES = Yes

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