RPTED NEAR LOSS OF SEPARATION BTWN 2 ACFT AT THE SAME ALT ON OPPOSITE DIRECTION RTES. TCASII AND RPTR EVASIVE ACTION TAKEN. RADAR OPS IN DARC MODE DUE TO NAS COMPUTER FAILURE.

Narrative

I WAS WORKING THE RADAR POS AT THE DAYTON HIGH SECTOR DURING A VERY BUSY PERIOD OF TFC. I HAD A TRACKED (HDOF CTLR) HELPING ME AND A D SIDE. THE COMPLEXITY OF THE TFC WAS VERY HIGH DUE TO THE LOSS OF THE MAIN HOST COMPUTER (WE HAD BEEN WORKING DARC/HOST FOR 2 DAYS) AND TURB CAUSING MANY ACFT TO REQUEST LOWER ALTS. SO MUCH OF MY ATTN WAS ON THE MANY ACFT ASKING FOR A DIFFERENT ALT THAT I DIDN'T SEE THE 2 ACFT INVOLVED RUNNING TOGETHER. IN THE DARC/HOST MODE CONFLICT ALERT DOES NOT WORK AS WELL AS MANY OTHER FEATURES AVAILABLE IN NAS. THE FIRST I KNEW OF A PROB WAS WHEN ONE OF THE ACFT RPTED A TCASII RA AND THAT HE WAS CLBING TO FL280. I THEN SAW THE PROB AND DSNDED THE OTHER ACFT. DURING HIS READBACK HE ALSO STATED HE HAD A TCASII RA TO DSND. I FEEL THE SECTOR WAS MUCH TOO BUSY TO WORK WITHOUT THE NAS COMPUTER WORKING. NEITHER I; THE TRACKER; THE D SIDE NOR A SUPVR; WHO WAS QUICKLOOKING THE SECTOR; SAW THE TFC CONFLICTION. HAD THE NAS SYS BEEN WORKING; CONFLICT ALERT WOULD HAVE ACTIVATED IN PLENTY OF TIME TO RESOLVE THE PROB. IN HINDSIGHT I PROBABLY SHOULD NOT HAVE WORKED SO HARD TO HELP THE ACFT IN CHOP BUT JUST CONCENTRATED ON SEPARATION AND SAFETY ALERTS. I FEEL ALSO FLOW CTL SHOULD HAVE PUT OUT MORE FLOW RESTRS AND RTED SOME OF THE ACFT AROUND ZID AIRSPACE. THE CTR OBTAINED THE HIGHEST TFC COUNT EVER ON THIS DAY. THIS SHOULD NEVER HAVE HAPPENED WHILE OPERATING IN DARC/HOST.