If you use Time Machine to make regular backups, I’m sure that you have and use my free check and diagnostic utility T2M2. I have a new version for you, which has three improvements:

• When the T2M2 app opens, it now checks whether the current user has admin privileges. To be more precise, whether they are a member of the admin group (80). If they aren’t, it displays an alert, and when you dismiss that, the app quits. This is because T2M2 performs analyses on the log, and those are only available to admin users. One side-effect of this is that, from version 1.9 onwards, you can’t use RunT2M2 to launch T2M2 from a non-admin account, something which has become increasingly unreliable anyway. This new test should be a better way to ensure that you don’t inadvertently try to use T2M2 when logged in as a ‘regular’ user.
• When run in Catalina, T2M2 harvests and displays additional information about the methods used to determine what to back up on different volumes. This is detailed below.
• Minor improvements in the form of additional emoji have been added to the text display, to make any problems clearer.

As I have detailed elsewhere, macOS 10.15 introduces some interesting changes in Time Machine. Among these is the fact that, when making a backup, Time Machine considers different strategies for detemining what needs to be backed up. The rules are as follows:

• If that volume hasn’t been backed up before, it performs a first run backup, in which the entire contents are copied.
• If backing up the Recovery volume, a ‘deep scan’ is performed on every subsequent occasion.
• For other APFS volumes, it chooses whether to use the hidden FSEvents database, or if that isn’t suitable, it may calculate the differences between two snapshots instead.
• For HFS+ volumes, only the FSEvents database is available.
• When other methods fail, or aren’t available, a deep scan is performed.

T2M2 now reports which strategies were used, on a volume total basis. For a Mac which is just backing up its internal storage, which has System, Data and Recovery volumes to be backed up, that represents three volumes each hour. After two hours of backups, you’d therefore expect T2M2 to report that 6 volume backups were made, of which 2 were deep scans (the Recovery volume), and 4 used FSEvents (the System and Data volumes).

These decisions are made prior to starting the backup process itself. If Catalina appears to get ‘stuck’ making a backup, you can then run T2M2 and inspect those totals to get an estimate of the strategy being used for the current volume. That can, in turn, give you a good idea if one of these methods is the cause of the problem. You can then check using my free log browser Consolation 3.

T2M2 versionn 1.9 is now available from here: t2m219
from Downloads above, from its Product Page, and through its auto-update mechanism.

Tomorrow I start a new series of articles looking at Time Machine, diagnosing its problems, and understanding how to fix them.