You are performing an ONTAP upgrade with an intercluster data protection SnapMirror relationship in this...

Before performing a nondisruptive upgrade (NDU) of ONTAP with an intercluster data protection SnapMirror relationship, you should quiesce the SnapMirror operations and upgrade the destination cluster first. Quiescing the SnapMirror operations prevents data inconsistency and ensures that the source and destination are at the same point-in-time. Upgrading the destination cluster first ensures that the destination is compatible with the source and can resume the SnapMirror transfers after the upgrade. References :- Prepare SnapMirror relationships for an ONTAP upgrade, TR-4015: SnapMirror Configuration and Best Practices Guide for ONTAP 9.11