Hello,
cDOT or 7-Mode ?
But I think your problem is un Snpmirror options on destination Volume
Normaly, a Snapmirror Volume have un option to lock any resieze, you con change it by vol option commande, but carfull it could be hazardous for the next sync of snapmirror.
You can try to modify it just on the FLEXClone but I not sure it's possible.
The last solution If you have some space @ destination is tthe flex split to have a real volume and @ this time you do anythinks you want on this new vol
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