The DELPHI experiment has already collected 2.5 million Z ⁰ decays with the ring imaging Cherenkov detector (RICH) operational. This detector, covering most of the solid angle, is designed to perform π/K separation from 0.8 to 20 GeV/c and K/p separation from 0.8 to 35 GeV/c. After a brief detector description we discuss the actual operating conditions, the data monitoring and the signal treatment. The collected data from Z ⁰ decays and the detector response to signals from the calibration system are used to evaluate the performance of the RICH system.