The after-image files must be isolated to provide maximum protection from media loss. If you lose a database or a before-image drive, you can replace the drive, restore your backup, and use the after-image file to restore your database. If you lose an after-image drive, you can disable after-imaging and restart the database. You will only lose active transactions if the after-image extents are isolated from the rest of the database. Sometimes this is difficult to do because you might have several file systems accessing the same physical drive, but the isolation must be at the device and file system levels.