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taking down a software image, and planned software outages are the predominant
form of software image outages in any case. Forming a single CPC sysplex allows
software updates to occur in a "rolling" IPL fashion, maintaining system availability
throughout. An LPAR cluster is one example of a single CPC sysplex which has
significantly improved system availability over a single LP. For additional benefits
provided by an LPAR cluster using IRD technology, see redbook z/OS Intelligent
Resource Director, SG24-5952.
Coupling Facility Nonvolatility
Continuous availability of the transaction processing workload in a coupling facility
configuration requires continuous availability of the shared structures in the coupling
facility. To help ensure this, you must provide an optional backup power supply to
make coupling facility storage contents nonvolatile across utility power failures.
Nonvolatility Choices
The following table indicates the optional nonvolatility choices available and their
capabilities:
Setting the Conditions for Monitoring Coupling Facility
Nonvolatility Status
In addition to installing an optional backup power supply to help ensure continuous
availability, you must also set the conditions by which the coupling facility
determines its volatility status. Software subsystems with structures defined in the
coupling facility can monitor this status. Use the coupling facility control code MODE
command as follows:
v MODE NONVOLATILE sets coupling facility volatility status to nonvolatile and
v MODE VOLATILE sets coupling facility volatility status to volatile and should be
The coupling facility MODE setting is saved across power-on reset and activation of
the coupling facility. You can use online help from the Operator Messages panel to
get additional information on coupling facility control code commands.
Coupling Facility Mode Setting
The following table summarizes the relationship between the coupling facility MODE
setting, and the resulting conditions you can expect if utility power fails at your site.
Table 2-5. Nonvolatility Choices for Coupling Facility LPs
Nonvolatility Choices
Uninterruptible power supply (UPS) (See Note 1)
Internal Battery Feature (IBF)
Local Uninterruptible Power Supply (LUPS) (See Note 2)
Notes:
1. Optional uninterruptible power supply (UPS) provides a secondary power source for use
during extended utility power outages allowing continuous coupling facility operation.
2. The optional Local Uninterruptible Power Supply supports 0 to 18 minutes of full power
operation.
should be used if a floor UPS is available to the CPC. Coupling facility control
code does not monitor the installation or availability of UPS but maintains a
nonvolatile status for the coupling facility.
used if no backup power supply is installed and available. Coupling facility control
code maintains volatile status for the coupling facility even if a backup power
supply is installed and available.
z9 BC
Yes
Yes
Yes
Chapter 2. Planning Considerations
z9 EC
Yes
Yes
Yes
2-45
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