LGT CLBS ABOVE ASSIGNED ALT WHEN TCASII CAN'T FIGURE OUT IF CLBING TFC INTENDS TO LEVEL OFF 1000 FT BELOW.

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ON APCH INTO PDX; WE WERE ON DOWNWIND LEG; LEVEL AT 10000 FT; 210 KIAS; WITH AUTOPLT ENGAGED. WE RECEIVED AN RA ON TCASII COMMANDING A RAPID CLB TO AVOID AN IMPENDING MIDAIR. SINCE THIS IS A MANDATORY CLB WHEN TFC HAS NOT BEEN POINTED OUT BY THE CTLING AGENCY; NOR HAS VISUAL CONTACT BEEN MADE WITH THE CONFLICTING ACFT BY THE FLC; I (THE CAPT) DISENGAGED THE AUTOPLT AND BEGAN AN IMMEDIATE CLB OUT OF 10000 FT; AND STARTED LOOKING FOR THE ACFT INDICATED ON TCASII. THE FO SIMULTANEOUSLY CALLED APCH CTL AND INFORMED THE CTLR OF OUR ACTIONS. BEFORE REACHING 10300 FT; WE VISUALLY SPOTTED THE ACFT BELOW US IN A 'NO CONFLICT' SIT HDG AWAY FROM US 90 DEGS TO OUR COURSE. THE CTLR THEN ADVISED US THAT THE TFC WAS UNDER HIS CTL AND WAS ASSIGNED 9000 FT AND WAS; IN FACT; LEVELING OFF AT THAT ALT. THE ACFT WAS A BIZJET WITH A HIGH RATE OF CLB AND TRIGGERED OUR TCASII WHICH COMMANDED A CLB FOR EVASIVE ACTION TO AVOID AN APPARENT NEAR MISS. IN REALITY; WE WERE NEVER CLOSER THAN ABOUT 1200 FT VERT AND 1/2 MI HORIZ. PLEASE NOTE THAT NO 'TA' WARNING WAS EVER GIVEN BY TCASII; NOR WAS TFC POINTED OUT BY APCH CTL PRIOR TO THE RA AND THE 'CLB' COMMAND BEING GIVEN BY TCASII. I DO NOT KNOW OF A SOLUTION TO THIS PROB IN A HIGH DENSITY TFC SIT. CTLRS ARE JUST TOO BUSY TO ISSUE TFC IN EVERY SIT WHERE A TCASII MAY BE TRIGGERED AND NO IMPENDING CONFLICT EXISTS. OUR EQUIP IS NOT SOPHISTICATED ENOUGH TO READ THE PLT'S MIND IN THE CONFLICTING ACFT AND DETERMINE WHETHER OR NOT HE WILL DO WHAT A CTLR TELLS HIM. UNTIL THAT DAY; PLTS AND CTLRS MUST DO THEIR BEST TO STAY ALERT AND AWARE!