State of the backup after an error

If there was an error with one of the files in the backup is the rest of the backup revision still fine?
I.e. right now, I had the situation that my Outlook .pst file was locked as Outlook was open, and so I got an access error as the file could not be backed up.

I’m fine if the file that caused the error is not backed up and I know I can use the volume shadow copy feature but my interest is more about what happens when something goes wrong in general. I.e. when VSS can’t solve the problem …

If the file can’t be opened, then the backup will continue with the file to be skipped.

If the file can be opened but can’t be read, then the backup will abort.