LCL CTLR AT OAK CLRED ACFT TO LAND ON CLOSED RWY.

Narrative

I WAS WORKING THE LCL CTL POS AT THE N TWR OF OAKLAND ARPT. I HAD TAKEN OVER THE CIC DUTIES AT THE SAME TIME AS RELIEVING AN INDIVIDUAL FROM THE GND CTL POS. I WORKED FOR 1 HR AT GND CTL UNDER NORMAL CONDITIONS. THE FACILITY WAS SHORT STAFFED WITH JUST 2 CTLRS. WHEN AN ADDITIONAL CTLR ARRIVED; THEY RELIEVED ME FROM GND POS AND I TOOK A BATHROOM BREAK AND RETURNED TO THE LCL POS (TWR) TO RELIEVE THE CTLR GOING HOME. I TOOK THE BRIEFING CONSISTING OF ACFT ONLY. ON TAKING POS; AN ACFT INBOUND FROM THE N WAS GIVEN LNDG CLRNC ON RWY 27L. THE ACFT WAS INADVERTENTLY CHANGED TO RWY 27R. I WAS NOT AWARE THAT RWY 27R WAS CLOSED TO LNDG ACFT. ACFT HAD BEEN DEPARTING WHEN I WAS WORKING GND. THE ACFT LANDED OVER A CONSTRUCTION CREW IN THE CLR ZONE (CREW WAS NOT ON RWY). THIS WAS MY FIRST DAY BACK; FROM A 10 DAY VACATION; IN THE N TWR. THERE WERE MANY CONTRIBUTING FACTORS: 1) POOR STAFFING. 2) MULTIPLE DUTIES -- CIC AND WORKING POS. 3) POOR OR INADEQUATE PLACARDS. 4) POOR OR INCOMPLETE BRIEFINGS ON BOTH RELIEVED CTLRS (SINCE I HAD NOT WORKED). 5) MY INABILITY TO RECOGNIZE AND BREAK A CHAIN OF EVENTS DUE TO DISTR OF DATA ENTRY; PHONES; STAFFING; POS AS CIC. I WAS INFORMED OF THE INCIDENT AT XA00 ON MAY/MON/04.