The Db is a logarithmic measure referred to something in the electronic measures field. If the references are (example) Volts or Watt the db for the measures maybe DbV or DbW.
In the disc cutting techniques, many years ago, was assumed the standard that 0Db was referred to the real measure system for the level can be cut on an analogue disc that is an optical system called "Meyer Light Pattern" (from his author) that measures, with particular mathematical formula, the "velocity" of the modulation in the groove.
This standard was assumed "0Db" at about 5 to 7 cm/sec for a stereo cut and 11cm/sec for a mono cut.
Now, after many years, with the new cutting technologies (even though new means at least 20 years old!) some modifications to this "0Db" ref have been accepted in the world:.. the last European standard took like "0Db" reference the level of +6 Db ref to the "0" US ref level that is +4Db over the "0Db" old but standard true ref. at the velocity of 5cm/sec. All this can get confusing! But on the disc it is the same thing.. over the maximum level capacity it is not possible to cut!! This is "0/+6 or +12". We took as reference the publications of the AES-Audio Engineering Society, Shure reference "ERA IV",DIN (Deutsche International Norm) discs; so, referred to these standard recording levels of 0Db@5cm/sec we can cut at the maximum level of +12Db if possible (+2Db European new reference/+8 US standard).
We advise you to not make cuts over this "0" Db European standard to avoid needle jumps and distortion.
The maximum time possible each side on a 12" is about 25min but at low volume level (-10Db EU standard).