It should happen before disk access across the CI bus is even possible. I think we'll have to agree to disagree on this one :-) I've just booted my Vaxstation 2000 into an NI cluster with my Vaxstation 3100. I gave the commands: NCP SET CIRCUIT SVA-0 STATE OFF NCP SET CIRCUIT SVA-0 STATE ON on each node. The only effects were an opcom message complaining about adjacency down and the loss of my decnet connections. Both nodes continued to function quite happily while the circuit was off. No crash. Anyway, it looks like avoiding issueing the SET CIRCUIT STATE OFF command by making the changes to the permanent database and rebooting was a good way of sidestepping the problem. Hopefully the bug is only triggered when SET CIRCUIT STATE OFF is issued in Marks setup. Apologies to gerry77. I missed your reply earlier and ended up repeating much of what you said. Regards, Peter Coghlan.