6947ch02.fm Draft Document for Review April 7, 2004 6:15 pm
52 IBM eServer zSeries 990 Technical Guide
Additional SAPs are characterized first, then CPs, followed by IFLs, ICFs and zAAPs. For
performance reasons, CPs for a logical partition are grouped together as much as possible.
Having all CPs grouped in as few books as possible limits memory and cache interference to
a minimum.
When an additional book is added concurrently after Power-on Reset and new logical
partitions are activated, or processor capacity for active partitions is dynamically expanded,
the additional PU capacity may be assigned from the new book. It is only after the next
Power-on Reset that the processor unit allocation rules take into consideration the newly
installed book.
Transparent CP, IFL, ICF, zAAP, and SAP sparing
Characterized PUs, whether CPs, IFLs, ICFs, zAAPs or SAPs, are transparently spared,
following distinct rules.
The z990 server comes with 2, 4, 6, or 8 standard spare PUs, depending on the model. CP,
IFL, ICF, zAAP, and SAP sparing is completely transparent and requires no operating system
or operator intervention.
With transparent sparing, the application that was running on the failed processor is
preserved and will continue processing on a newly assigned CP, IFL, ICF, zAAP, or SAP
(allocated to one of the spare PUs), without customer intervention. If no spare PU is available,
Application Preservation is invoked.
Application preservation
Application preservation is used in the case where a processor fails and there are no spare
PU available. The state of the failing processor is passed to another active processor used by
the operating system and, through operating system recovery services, the task is resumed
successfully— in most cases without customer intervention.
Dynamic SAP sparing and reassignment
Dynamic recovery is provided in case of failure of the System Assist Processor (SAP). In the
event of a SAP failure, if a spare PU is available, the spare PU will be dynamically assigned
as a new SAP. If there is no spare PU available, and more than one CP is characterized, a
characterized CP is reassigned as a SAP. In either case, there is no customer intervention
required. This capability eliminates an unplanned outage and permits a service action to be
deferred to a more convenient time.
Sparing rules
The sparing rules for the allocation of spare CPs, IFLs, ICFs, zAAPs, and SAPs depend on
the type of processor chip on which the failure occurs. On each MCM, two standard spare
PUs are available. The two standard SAPs and two standard spares are initially allocated to
dual core processor chips. Table2-3 illustrates the default PU-to-chip mapping.
Note: Even in a multi-book system, a book failure is a CPC system failure. Until the failing
book is repaired or replaced, Power-On Reset of the z990 with the remaining books is not
supported.