MLG ON ARR; HAS TCASII RA TO DSND.

Narrative

FLYING STANDARD ARR TO LAX AND ASSIGNED 16000 FT BY ZLA (LEVEL AT 16000 FT). CTR ADVISED 2 TARGETS (BOTH IFR OR IN CONTACT WITH CTR). ACFT #1 CLBING THROUGH OUR ALT AND PASSING OFF OF OUR L SIDE; ACFT #2 AHEAD OF US AND CLBING TO LEVEL BELOW OUR ASSIGNED ALT (CLBING TO 15000 FT; I BELIEVE). #1 TFC CALL WAS PICKED UP VISUALLY BY CAPT (PNF) AND INDICATED ON TCASII (VISUAL ACQUISITION DIFFICULT DUE SUN ANGLE). SEPARATION (VISUALLY) WAS SUBSTANTIAL WITH NO REQUIREMENT FOR ACTION. HOWEVER; TCASII WENT INTO RA AND COMMANDED APPROX 2000 FPM DSCNT. ATC WAS ADVISED THAT WE WERE DSNDING DUE TO TCASII. AT APPROX 15500 FT TCASII RA CEASED AND ORIGINAL ASSIGNED ALT WAS RESUMED (16000 FT). SHORTLY AFTER RETURNING TO 16000 FT THE CAPT (PNF) VISUALLY ACQUIRED THE PREVIOUSLY RPTED ACR (#2 TARGET) PASSING SEVERAL THOUSAND FT BELOW (NO TCASII DISPLAY). ATC RESPONDED TO THE CALL OF INITIAL DSCNT FROM 16000 FT (ASSIGNED) BUT APPEARED TO BE SOMEWHAT CONFUSED (NORMAL) WITH THIS UNEXPECTED ACTION. ATC LATER INDICATED THAT WE HAD DSNDED INTO 'RESERVED' AIRSPACE (PROBABLY RESERVED FOR SEPARATION BTWN US AND THE ONCOMING JET). GENERAL: NO 'NEAR MISS' CONDITION APPEARED TO EXIST; HOWEVER; THE #1 TARGET ACFT DID GET CLOSE ENOUGH TO CAUSE RA ON TCASII. THE MOST SERIOUS POTENTIAL FOR COLLISION APPEARED TO BE FROM DSNDING INTO AN ONCOMING CLBING ACFT (DISTANCE BTWN PLANES PRECLUDED THIS OCCURRENCE). VISUALLY (VMC) THIS RA WAS SOMEWHAT 'INCONVENIENT.' IN IMC IT WOULD HAVE BEEN 'DAMN UNCOMFORTABLE.'