FLC OF DH8 DEVIATED FROM RTE/ALT CLRNC DUE TO A TCASII RA. RPTR ALLEGES NO TRAINING OR GUIDANCE WAS RECEIVED ON LATERAL DEVS DUE TO TCASII RA'S.

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WHILE WORKING A DH8 INBOUND TO MHT AT 4000 FT FROM THE SW; I ISSUED TFC ON A VFR TARGET IN HIS 1 O'CLOCK POS; APPROX 6 MI; MANEUVERING AT 4300 FT. HE INDICATED HE WAS LOOKING. I UPDATED THE TFC CALL WHEN BOTH TARGETS WERE ABOUT 2 MI APART. NO VECTOR WAS REQUESTED. WHEN THE TARGETS WERE 1 MI TO 1 1/2 MI APART; THE DH8 TURNED N AND DSNDED APPROX 500 FT. HIS TURN PUT HIM IN PROX OF OTHER VFR TFC INDICATING 3100 FT. AT THAT TIME HE (DH8) ADVISED HE WAS RESPONDING TO SEVERAL ALERTS. I ISSUED A TA ON THE 3100 FT TFC. THIS SIT WAS RPTED TO THE SUPVR. I REQUESTED TO RPT THIS SIT ON A TCASII FORM. I WAS ADVISED THIS WAS NO LONGER REQUIRED. I FEEL A LATERAL DEV FROM AN ATC CLRNC IS UNSAFE AND NOT THE PURPOSE TCASII WAS INTENDED FOR. I RECEIVED NO TRAINING OR GUIDANCE ON HANDLING ACFT THAT DEVIATE LATERALLY ON A RESOLUTION OR TA. I BELIEVE THIS TO BE AN UNSAFE PRACTICE. I HAVE RPTED THIS SIT BEFORE AND IT SEEMS TO BE IGNORED. THE PROC OR RECOMMENDATION TO REQUEST A VECTOR AROUND TFC HAS BEEN AROUND LONGER THAN TCASII. IT SEEMS TO BE FORGOTTEN.