What was found
LEFT FMC FAILURE SHORTLY AFTER LEVEL OFF AT FL390. VTK AND MAP CAUTION FLAGS ON CAPTAINS MAIN NAVIGATION DISPLAY PANEL. FOLLOWED QRH PROCEDURE PLACING THE FMC SWITCH ON THE OVERHEAD PANEL TO BOTH FMC'S ON RIGHT. VTK AND MAP FLAGS EXTINGUISHED AND NORMAL OPS RESTORED. CONTINUED FLIGHT WITH BOTH FMC'S OPERATING OFF THE RIGHT SIDE. LNAV AND VNAV WERE AVAILABLE IN THE CONFIGURATION. CYCLED A/C POWER. ACCOMPLISHED FIM 34 61 TASK 801. NO FAULTS NOTED. GROUND VERIFICATION SUCCESSFUL.