This means that if I keep TM activated most of the time without the external HD connected I will step by step fill my local HD with snapshots. How to clean this local snapshots ? Will they be deleted if I connect the external HD and format it to restart a new TM and in the future never leave TM active without the external HD connected ?
I know it will not be a safe way to use TM but this will not be the problem because it is reduntand: I have an iMac at home with its own TM Disc always active, a MBP which is every 2-3 days exactly synced with the iMac and has exactly the same Apps and data. The TM disc for the MBP is in a different location and connected only at WeekEnds, and every month I make a manual backup of both Macs on 2 different discs. With the Thunderbolt connection it is fast.
Thanks for yoyr time Linc.
You don't need to worry about filling the volume with local snapshots. They're deleted automatically when they expire, or when free space on the volume falls below a certain level.
The Finder reports the space occupied by the snapshots as "available," which it is. Think of the snapshots as putting available space to good use, instead of wasting it. It's still available for new files.