That's one very large file!
Performance, Troubleshooting S60 3rd Edition, S60 5th EditionQ. I have recently been doing a clean up on my microSD card and have come across a very large file in one directory: /private/101ffc31/glxmdstn. My PC doesn't recognize it and it isn't visible in my phone's file browser. The file is a whopping 140MB. What purpose does it have? Is it safe to delete it? Maybe it's obsolete data?
A. File 'glxmdstn' is hidden because it's a data file used by the operating system for caching thumbnails of photos and videos on your device. However, as you probably suspected, with use this database can get quite large and there doesn't seem to be a way to compress or optimise it. With today's huge microSD cards, 140MB is unlikely to be a showstopper, but I'm sure you'll notice some improvement in performance by getting rid of it anyway.
Either delete the file using a card reader or put your phone in 'Data transfer' (or similar) mode, if it's not already, and then do the same. Don't worry, the Gallery/Photos applications will recreate the database as needed – and you'll save at least 100MB of disk space in the process!
(This original text of mine was originally published in Smartphone Essentials magazine and re-purposed here with kind permission)