Don't need attributes, but what if read only?

[Darius1968]

I know that common xmp metadata (encompassing both, exif & iptc) is already stored in the database, as well as in the actual file itself.  What if, however, someone gives me some scanned images on a read-only medium (CD/DVD ROM, Blu-Ray, etc.)?  I could make changes (I suppose) to the metadata of the file, because they would be stored inside the database, with the flag set to the effect that the file has pending metadata write-back.  However, how would I turn this flag off, given that I can't write the data back to a read-only file that is originally from the DVD-ROM, and I don't wish to copy that file to my hard drive storage? 

[Mario]

Yes, you can manipulate metadata even for files on read-only media.
And IMatch will then mark the files as having a pending write-back. It has to.
If this disturbs you I see only these possibilities:

a) Don't modify metadata for files which are read-only forever

b) Switch to a file window layout which does not show icons

c) Move your files from a DVD/CD-ROM to a writable media (USB stick or similar).
This will allow IMatch to write-back the changed metadata. And, since DVD/CD-ROM are prone to bitrot after 5 or more years, this would also be safer for your files.

[Darius1968]

"If this disturbs you I see only these possibilities:"
No, the icon doesn't disturb me at all, as long as I know that having these so called, "pending metadata write-back" files in my database in that state, indefinitely doesn't do anything to compromise performance. 

[Mario]

This does not impact performance. Calculating the "Pending Write-back" collection will take a bit longer.
And you will run into issues when you enable the background write-back - because IMatch will then repeatedly try to write-back the off-line/read-only files.