AN ACR LGT WAS CONFUSED BY TCASII INSTRUCTIONS. HE RECEIVED COMMANDS BOTH 'DON'T CLB' AND 'DON'T DSND' WHILE BEING SANDWICHED BTWN 2 ACFT.

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WE WERE ON RADAR VECTORS TO A VISUAL APCH TO RWY 34R SEA ON STEP-DOWN DSCNT FROM 9000-6000 FT HDG 270 DEGS. PASSING HDG 230 DEGS; WE CALLED TFC AT 11-12 O'CLOCK; TCASII SHOWED TFC AT 6000 FT. WE WERE OUT OF 6500 FT; DSNDING! APCH CTL TOLD US TO MAINTAIN 6500 FT. WE WERE AT 6300 FT. ACR X TFC PASSED 300 FT BELOW AND LESS THAN 1000 FT TO THE L OF US. WE RECEIVED RA 'DON'T DSND' FOLLOWED BY SECOND RA 'DON'T CLB' BECAUSE OF 7000 FT TFC ABOVE US. WHILE THE RA'S WERE GOING OFF; APCH GAVE US A R TURN TO HDG 010 DEGS TO INTERCEPT RWY 34R VISUAL. IN MY OPINION; THERE WERE 2 CAUSES TO THE PROB: 1) EARLY ON; APCH CTLR BECAME INVOLVED IN LENGTHY CONVERSATION WITH LIGHT ACFT AND DID NOT FORESEE THE DEVELOPING PROB; THEN TRIED TO DIG HER WAY OUT WITH ALL THE HDG CHANGES. 2) ACR X WAS CLRED FOR A VISUAL TO RWY 34L. THEY THEN PROCEEDED ACROSS THE FINAL FOR RWY 34L AND RWY 34R AND DID NOT DSND AT ALL. ALL IN ALL; I DO NOT THINK 6300-6500 FT IS THE PLACE TO PRACTICE STEEP TURNS TO AVOID TFC AT 6000 FT AND 7000 FT. THIS WAS THE FIRST FOR-REAL RA I HAVE SEEN SINCE SYS WAS INSTALLED AND THE SECOND RA WAS ONLY 5 SECONDS LATER.