ZOA CTLR EXPERIENCED OPERROR AT APPROX FL330 WHEN ACR WITH SIMILAR FLT NUMBERS INITIATED CLIMB THROUGH OCCUPIED ALT.

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I WAS WORKING SECTOR 32 IN ZOA AREA N. I WAS IN CTL OF ABOUT 15-17 ACFT AT THE TIME. I HAD AN ACR X ON FREQ AND AN ACR Y AS WELL. I HAD ACFT Z ON FREQ IN LEVEL FLT AT FL340 HDG NBOUND. WHEN ACR Y CHKS ON FREQ I INITIALLY CLB HIM TO FL310 BECAUSE OF TFC AT FL320 IN OPPOSITE DIRECTION. AFTER THIS CONFLICT WAS RESOLVED THEN I CLB HIM TO FL330 BECAUSE OF ACFT Z BEING AT FL340. AT THIS TIME ACR X HAS CHKED IN AND I INITIALLY CLB HIM TO FL270 BECAUSE OF TFC SBOUND AT FL280. AT THIS POINT I HAD DECIDED TO PUT A J-RING ON ACR Y BECAUSE OF THE PROX THAT HE WAS GOING TO HAVE WITH ACFT Z. I USED THE J-RING AS A REMINDER NOT TO CLB ACR Y BECAUSE OF ACFT Z. AT THIS POINT THE CONFLICT BTWN ACR X AND HIS TFC WAS RESOLVED; AND I ISSUE A CLRNC FOR CLB TO ACR X TO FL350. ABOUT 5 MINS MY RADAR ASSOCIATE REALIZED THAT ACR Y WAS CLBING THROUGH FL330 AND TOLD ME ABOUT IT. I ASKED ACR Y IF HE WAS LEVEL AT FL330 (AT THIS TIME THE DATA BLOCK WAS INDICATING FL332) AND HIS REPLY WAS 'NEGATIVE; WE WERE ISSUED A CLB TO FL350; WE ARE CLBING FL350.' I REPLIED; 'NEGATIVE ACR Y; YOU WERE ISSUED FL330; DSND AND MAINTAIN FL330 IMMEDIATELY.' WHEN THE PLT ANSWERED BACK YOU COULD HEAR A LOUD ALARM IN THE BACKGROUND. AT THIS TIME SEPARATION BTWN ACR X AND ACFT Z WAS LOST.