Yes, I know about D of Q. I used to run the archive on a Computer system and these ran on expensive Optical disks, which had to run daily or the disks filled up. The company stores held my supply, 3 boxes of 10 disks (D of Q=10). I used to order a box at a time, about once a week. A new stores manager took over and decided that it should be 3 disks only, but didn't tell anyone. I put my usual order of a box of 10 disks through and was told that it couldn't be supplied. My reply was that the entire telephone reporting system on the Vodafone network was about to stop unless I had the disks the next day. They changed the D of Q very rapidly.