I would advise to make the update after hours to ensure nothing is running on the iSeries other than Mimix. When all your links are up to date with no lag time, end mirroring then update the Target(?) ip address. Ping afterwards to insure the Source can see the new Target ip. I believe there is also a function in Mimix that when selected will verify the ip. After verifying, make the appropriate change in Mimix to point to the new Target ip. Mimix should start with no issues since there was no lag time.