Catalogs contain information about objects that were backed up during a backup job and that are contained in the backup set created from that job. True image catalogs for incremental backups contain additional information about all selected files and directories that were on the volume at the time of the backup job and about the latest backed-up versions of those objects. This additional information creates a true image of the entire volume as of the time of the backup job, even though the incremental backup job backed up only the changed files. In addition, true image catalogs track deleted files, so files that were deleted before the time of the incremental backup are not restored.
About collecting additional information for synthetic backup and true image restore