ACR ON INITIAL CLB IS VECTORED TOWARD CIRCLING VFR TFC. RECEIVES TCASII TA; THEN RA. RESPONDS WITH CLB WHICH PRECIPITATES RA FROM TFC ABOVE.

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WE DEPARTED RWY 22R AT BOS AT XX46 LCL. OUR DEP INSTRUCTIONS WERE AN INITIAL CLB TO 3000 FT WITH A R TURN AFTER TKOF TO 300 DEGS. AFTER CONTACTING DEP CTL; WE WERE CLRED TO 4000 FT ON THE SAME HDG. ATC THEN ISSUED A TA FOR VFR TFC AT 11 O'CLOCK 2-3 MI AT 3500 FT CIRCLING. AT ALMOST THE SAME INSTANT WE GOT A TCASII TA FOLLOWED IMMEDIATELY BY 'MONITOR VERT SPD' FOLLOWED BY A TCASII RA -- CLB. ATC AT THE SAME TIME WAS GIVING US A R TURN TO 360 DEGS; MAINTAIN 4000 FT; DIRECT MANCHESTER MHT WHEN ABLE. I DID NOT HAVE THE TFC IN SIGHT AND FOLLOWED THE TCASII CLB RA. THE RESULT OF THE TCASII CLB CREATED ANOTHER TA FROM APCHING 5000 FT TFC. ATC DETERMINED THAT THE 5000 FT TFC HAD VISUAL CONTACT WITH US AND THEREFORE HE CONTINUED OUR CLB TO 5000 FT AND THEN A FURTHER CLB TO 12000 FT. THE INITIAL CONFLICT WAS CAUSED BY THE 3500 FT VFR TFC CIRCLING BELOW US; AS PER THE ATTACHED DIAGRAM; AS WE WERE CLBING TO 4000 FT. THE RA CAUSED ME TO CLB THROUGH 4000 FT CREATING A POTENTIAL CONFLICT WITH 5000 FT TFC. SINCE THIS IS THE SECOND SITUATION I HAVE ENCOUNTERED LIKE THIS IN THE LAST 4 MONTHS; I AM PERHAPS IN A POS TO SUGGEST THAT ATC BE GIVEN SOME TRAINING ON THE WORKINGS OF TCASII. VECTORING AN ACFT WITH A CHANGING VERT VELOCITY TO WITHIN 500 FT OF ANOTHER ACFT WILL CAUSE AN RA.