I find the FCOM descriptions of the FMGC and MCDU extremely hard to navigate and find the information necessary. To answer your question, though...
DSC-22_20-50-10 (Auto Flight - Flight Management - Controls and Indicators - MCDU Page Description)
--> FMS2 Honeywell
--> Aircraft Status Page
Once you've eventually found that, about half way down the page you find:
"CAUTION: Cycling the database erases the primary and secondary flight plans, as well as the stored data. The flight crew must never do this in flight."
Of course, if your airline does not have the Honeywell FMS2, your FCOM might say something different.