A B737-700 FMC DATABASE UPDATE ERRONEOUSLY CODED RNAV MANDATORY SPDS AS BELOW THE REQUIRED SPD RATHER THAN AT THE REQUIRED SPD.

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THE CURRENT FMC DATABASE APPEARS TO HAVE ADDED THE ABILITY TO CODE AIRSPDS 'B' (BELOW) MUCH LIKE IT HAS ALWAYS BEEN ABLE TO DO ALTS (A OR B). THE EAGUL2 ARR WAS CODED AS FOLLOWS: 'PAYSO 280B/240' 'PICHR 280B/160' 'HOMER 250B/120' 'QUENY 210B/080.' THE ALTS ARE CORRECT BUT THE AIRSPDS ON THE ARR ARE AT EXACTLY THAT AIRSPD; NOT BELOW. THIS CHANGE DID PREVENT US FROM GETTING ALL KINDS OF WARNINGS ABOUT 'UNABLE PAYSO AT 280 KTS' DUE TO OUR COST INDEX DSCNTS. BUT; IT DOES NOT SEEM CORRECT FOR THE ARR IN THE BOX TO DIFFER FROM THE PLATE. I ALSO FIND IT DISCONCERTING THAT SUCH A FUNDAMENTAL CHANGE HAPPENS TO OUR FMC WITH NO NOTICE OR INFO TO THE PLTS ABOUT IT. I THINK THAT THIS ARR (AND ANY OTHERS THAT GOT THE 'BELOW AIRSPD' TREATMENT) SHOULD BE PUT BACK TO ITS ORIGINAL AND CORRECT STATE AND THAT WE SHOULD DO A 280 KT DSCNT INTO PLACES LIKE PHX AND LAX RATHER THAN HAVE THE FMC ARRS BE MODIFIED TO SUIT OUR 'NEEDS' FOR A 261 KT DSCNT. I THINK WE'RE GETTING ENOUGH ATC QUERIES ABOUT OUR DSCNT SPDS WITHOUT HAVING OUR FMC INFO BEING WRONG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER STATED THAT AFTER THIS REPORT WAS FILED; HIS ACR NOTIFIED PILOTS ABOUT THE CODING ERROR AND CAUTIONED THEM TO DISREGARD CONSTRAINTS.