IBM 990 - Manual (Page 164)

152 IBM
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zSeries 990 Technical Guide
When issued from an operating system running as a guest under z/VM, the result
depends on whether the SET CPUID command has been used or not.
– Without the use of the set CPUID command, bits 0-7 are set to ‘FF’ by z/VM but
remaining bits are unchanged, meaning they are exactly as they would have been
without running as a z/VM guest.
– If the set CPUID command has been issued, bits 0-7 are set to ‘FF’ by z/VM and bits
8-31 are set to the value entered in the set CPUID command. Bits 32-63 are the same
as they would have been without running as a z/VM guest.
Table 6-5 shows the possible output returned to the issuing program for an operating
system running as a guest under z/VM.
Table 6-5 STIDP output for z990, VM guest
STSI Store System Information instruction
The STSI instruction returns the processor software model as a 16-byte character field. It
also returns the same processor type that is returned by the STIDP instruction and the full
serial number information.
The STSI instruction always returns the latest processor software model information,
including information about the new processor model after a concurrent model upgrade
has occurred. This is key to the functioning of CUoD, On/Off CoD, CIU, and CBU.
Channel to channel links
After a concurrent upgrade, the channel CPC Node-Descriptor (NED) information is not
updated until after a processor POR.
Additional planning may be required in a multisystem environment with CTCs linking different
processors. NED information, which includes serial number, machine type, and model, is
exchanged between systems on the CTC link. As a way to prevent cabling errors, CTCs will
go into a “boxed” state if the NED information changes without having taken the proper
actions. Boxed CTCs may impact XCF, VTAM®, IMS, and other software products.
Dealing with boxed CTCs in a multisystem environment is not new; it occurs during the POR
after traditional disruptive upgrades. However, in the case of a concurrent upgrade, the
node-descriptor information (model number) will not change until the next POR, which may
be months after the actual upgrade. At that time, the customer needs to be prepared to deal
with the boxed CTCs. It is important to consider and prepare for the case where, during an
unplanned POR of the upgraded process, the CTCs become boxed.
The boxing of CTCs can be avoided if, during the concurrent upgrade, the CTC links between
systems are deallocated and then varied offline. However, when alternate communication
links are not available, this may be disruptive to applications.
Version
code
CPU identification number Machine
type number
LPAR
2-digit
indicator
Bit position 0-7 8-15 16-31 32-48 48-63
Without
set CPUID
command
x’FF’ LPAR ID 4-digit number derived from
the CPC serial number
x’2084’ x’8000’
With
set CPUID
command
x’FF’ 6-digit number as entered by the
command SET CPUID = nnnnnn
x’2084’ x’8000’