Ever Changing Metadata Status

Question

I have LR 2 (on a Windows PC) set up to write all changes to XMP. Normally this works very well, but for some pictures the "Metadata Status" message in the Metadata panel constantly changes from "has been changed" to "..." to "Up to date" then back to "Has been changed" again. This happens in Library view when I am not touching the image.
It seems to happen randomly. If I exit LR and then return it has stopped.
The pictures in question seem to be fine, both to examine in LR, edit and also export.
Is this a known problem? Should I be concerned? It seems like a disk write to the image file or a data update to the catalog must be failing. But I have checked my hard drive and it seems healthy.
I wrote about this on my blog and even made an animated GIF http://bkkphotographer.wordpress.com/2009/09/17/the-case-of-the-ever-changing-status/

Answer 1

I’ve been playing with metadata and sidecar XMP files in order to try and learn the way Lr handles them. I’ve also read quite a bit about this subject and now I believe I understand the significance of these XMP files as an insurance in case anything goes wrong with the database, despite the fact that some relevant data is not included in the XMP file and would be lost in case of catalog (database) corruption.
So, I've done a very simple test:
- created a new catalog;
- imported 10 CR2 RAW files;
- immediately after importing they all displayed (quite obviously) a “Metadata Status: Up to date”;
- applied daylight as white balance to all of them in Quick Develop (“Metadata Status: Has been changed”); option to “automatically write changes to XMP” was off;
- saved the metadata to XMP sidecar files (“Metadata Status: Up to date”);
- closed Lr;
- deleted de XMP files.
When I reopened this catalog, Lr shows the Metadata Status as “Up to date”, even though the XMP files are gone. It’s quite understandable that Lr has no way of knowing that the XMP files no longer exist since they were deleted outside of Lr. But if one tries to recreate the XMP files by saving them again Lr shows briefly a message that it is writing the files but none are actually created. Interesting enough I never get the “sidecar file missing” warning.
I’ve found just two ways of recreating these XMP files after deleting them: either creating empty files with the appropriate names matching the CR2 files or changing some metadata (e.g. adding a caption or title to all photos) before saving the metadata.
OK, some might be asking why deleting the XMP files in the first place? Well, files do get deleted by accident sometimes and could also be lost due to file corruption.
What I would like to understand is if one has a catalog that doesn't use XMP sidecars and at some point they are created (by choice or mistake), is there a way of reverting back and not using them?
Am I missing something or Lr is a little bit weak in handling these XMP sidecar files?
Also, has anyone reproduced this on Lr 3 beta?
Any comments will be appreciated.