Re: How to tell which initiator has data on an RDF1+Mir symdev
Sean, I apologize for forgetting to mark this question as answered a year ago. Thank you for your thorough explanation and suggestions.
It turns out that all of my RDF1+Mir devices are CKD and mapped to ports on FICON directors. I can't find information about FICON directors and the ACLX bit, but I assume ports on FICON directors must work the same way as FA ports without the ACLX bit, as you describe in your second suggestion: all initiators zoned to the port can see all devices mapped to the port, which is the reason the devices aren't in initiator groups.
This invalidates my original question about listing the initiators that are using RDF1+Mir devices. In my environment, no RDF1+Mir is masked to any initiator.