I did all this process a week ago but after targeting the time machine backups to thue new drive, it makes new backups but does not find the loser backups contained in the previous drive. What am I missing here?
What is it you would like to do? Please explain the process you performed a week ago, and the reasons for it.
If you want to move Time Machine backups from one volume to another Apple provides these instructions: Time Machine: How to transfer backups from a current backup .... However, I find it simpler, easier, and faster to use Disk Utility's Restore function: Restore a disk using Disk Utility on Mac - Apple Support.
That's how I move a Time Machine backup history from a drive that has become too small for my needs to a larger one.
I followed the instructions you cited above in your first link.
I understand, but the problems you experienced with that method are the reason I advocate using Disk Utility's Restore function in lieu of Apple's method for copying Time Machine backups. Although Apple's method will work for all Time Machine backup devices, you are using directly connected hard disk drives. Using Restore will be simpler, easier, and faster.
Having said that... if Disk Utility is "freezing" or your cursor turns into the spinning rainbow "wait cursor" it usually indicates Disk Utility is having difficulty reading data from one of its mounted volumes. That implies disk corruption, which can't be fixed. In that case your first order of business should be to create at least one more Time Machine backup in addition to the one you are attempting to copy.
For the time being that additional Time Machine backup can be the new, larger drive you purchased. The older one may have suffered corruption, meaning its contents may no longer be reliable.
Since I upgraded to Mojave, my Mac (late 2012 27" iMac) is slower and is giving me a lot of headaches.
That's a separate question, but the first step in diagnosing it is to determine if the same problems occur in "Safe Mode": Use safe mode to isolate issues with your Mac. Start your Mac in Safe Mode, observe its operation for a little while, and then restart your Mac normally. Describe the differences you observe.
For the purposes of that test please disconnect the Time Machine disk.
It sounds as though the Time Machine backup disk was simply in use at the time. The obvious reason would be a Time Machine backup already in progress, but there could be others. I'd also connect both drives directly to your Mac, for reasons that I will explain.
You could obviate all those potential reasons by starting your Mac in macOS Recovery, and using its version of Disk Utility to restore the disk. That will preclude the problem of not being able to "unmount" the drives, which is required for Restore to work.
Restore does not care if Time Machine uses one or both drives in a directly connected fashion or by connecting them to an AirPort Extreme or Time Capsule... it simply duplicates their contents.
I needed to move my TM-backups history from a small drive to a new and bigger one I purchased for the purpose. I followed the instructions you cited above in your first link. Because I could not turn TimeMachine backup "off" by sliding the button in the TM-preferences window, I unchecked the "automatic backup" box. Then I unplugged the hard rive from the Airport extreme device and connected it directly to my Mac (runs Mojave) because the TM-drive did not showed in the volumes column of the Finder window. I formatted the new (bigger) drive in disk utility and then I tried to drag the contents from the old TM drive to the new: there were no folders "backups.backupdb" in it but 2 drive images ".sparsebundle" one for each Mac I backup in that TM volume plus a folder containing "Photos" from the laptop and a file named "SaveScanInformationAdvncd".
I dragged all that contents too the new drive and waited overnight.
The TM pref. window shows a backup in progress that has been stuck for a wee without any progress. I explored the TM app and did not find my previous history. With Mojave it seems that many things changed and I no longer can follow the tech instructions of Apple support. It is very confusing and frustrating.
Fortunately, the former volume (old) I had for TM-backups is still intact and I may be able to repeat this setting again but need help because, trying to Restore via Disk-U I cannot do it as Disk-U freezes and I cannot select any volume and do this recovery.
Since I upgraded to Mojave, my Mac (late 2012 27" iMac) is slower and is giving me a lot of headaches.
Thank you John for being with me. I tried today again following your instructions. This time I left the TM_backup disk in its place attached to Airport station while keeping the old drive (with former TM_backups intact) connected to my Mac. Everything failed and I received the following error message:
"Restoring “Time Machine Backups” from “Seagate3Tb”
Validating target...
Validating source...
Could not unmount volume "/Volumes/Time Machine Backups" (Resource busy)
The operation couldn’t be completed. (OSStatus error 16.)
Operation failed…"
I am lost. I don't know what to do.
Timemachine migration of data to a new drive
