IBM 990 - Manual (Page 222)

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zSeries 990 Technical Guide
Reduce the outage time to restart critical workloads from several hours to minutes.
8.6 Nondisruptive upgrades
Continuous availability is an increasingly important requirement for most customers, and
even planned outages are no longer acceptable. Although Parallel Sysplex clustering
technology is the best continuous availability solution for z/OS and OS/390 environments,
nondisruptive upgrades within a single server can avoid system outages and are suitable to
further operating system environments.
The z990 servers allow concurrent upgrades, meaning they can dynamically add more
capacity to the server. If operating system images running on the upgraded server need no
disruptive tasks to use the new capacity, the upgrade is also
nondisruptive . This means that
Power-on Resets (PORs), logical partition deactivations, and IPLs do not have to take place.
If the concurrent upgrade is intended to satisfy an “image upgrade” to a logical partition, the
operating system running in this partition must also have the capability to concurrently
configure more capacity online. z/OS and OS/390 operating systems have this capability.
z/VM can concurrently configure new processors and I/O devices online, but it does not
support dynamic storage reconfiguration.
Linux operating systems do not have the capability of adding more resources concurrently.
However, Linux virtual machines running under z/VM can take advantage of the z/VM
capability to nondisruptively configure more resources online (processors and I/O).
Processors
CPs, IFLs, ICFs, and/or zAAPs processors can be concurrently added to a z990 server if
there are spare PUs available on any installed book. The number of zAAPs cannot exceed
the number of CPs plus unassigned CPs on a z990 server.
Additional book(s) can also be installed concurrently, allowing further processor upgrades.
A processor upgrade cannot be performed when CBU or On/Off CoD is activated.
Concurrent upgrades are not supported with CPs defined as additional SAPs.
If reserved processors are defined to a logical partition, then z/OS, OS/390, and z/VM
operating system images can dynamically configure more processors online, allowing
nondisruptive processor upgrades. The Coupling Facility Control Code (CFCC) can also
configure more processors online to Coupling Facility logical partitions using the CFCC image
operations panel.
Important: Dynamic add/delete of a logical partition name allows reserved partition ‘slots’
to be created in an IOCDS in the form of extra Logical Channel Subsystem, Multiple Image
Facility (MIF) image pairs, which can be later assigned a logical partition name for use (or
later removed) via HCD concurrently.
Important: If the z990 STI Rebalance feature (FC 2400) is selected at server upgrade
configuration time, and effectively results in STI rebalancing, the server upgrade will be
disruptive and this outage must be planned. The z990 STI Rebalance feature may also
change the Physical Channel ID (PCHID) number of ICB-4 links, requiring a corresponding
update on the server’s I/O definition via HCD/HCM.