HP Integrity NonStop i NS2300 Planning Manual page 73

To prevent data loss during a utility power failure, you must manually disable the Write Cache
Enable (WCE) option on all the disk drive volumes. For information on how to disable the WCE,
see the SCF Reference Manual for the Storage Subsystem (G06.28+, H06.05+, J06.03+).
When the utility power is restored, you can enable the WCE.
During the utility power failure, the system can continue to run until the data center UPS
runs out of power or until it shuts down.
Non-Supported UPS Configurations 73