HP 10500 Series Configuration Manual page 128

At reboot, a subordinate device automatically synchronizes the master device's configuration and status
data. This process takes time. You must wait for the synchronization to complete before using the issu
load command on the subordinate device. To verify that the synchronization has completed successfully,
do the following:
Use the display device command to verify that all cards of the subordinate device are in normal
state.
Use the display mdc command to verify that all MDCs are in active state.
Use the display system internal ha service-group command to verify that the Action field is 0 for
each service.
After an ISSU, you must log in again to the device before you can configure the device.
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