Backup could not be completed
I thought Time Machine was supposed to delete old backups to make space when needed.
It is simply telling the bckupo failed because of not enough space.
What's up?
Mojave 10.14.6
There's actually lots of space on the backup disk ...
How much is "lots" and how much needs to be backed up?
You can answer that question if you wish, but TM calculated what needs to be backed up + an amount of "overhead" (perhaps 20% of that amount) ≥ "lots" even before it begins to delete older backups. Those older backups are not deleted until after a newer backup is created, always leaving an absolute minimum of one and only one complete, restorable backup.
The bottom line is that if Time Machines says it needs more space, then it needs more space.