They didn't strike up the band in San Francisco's Davis Symphony Hall on Wednesday night and they might not do so for a while. The San Francisco Symphony performance was canceled when the ensemble's 106 members called a strike late Tuesday after a lengthy negotiating session failed. Neither side would discuss details of the action because of a confidentiality agreement. It was not known whether the strike could affect the orchestra's planned Asian tour, scheduled to begin next month. Symphony musicians, members of Local 6 of the American Federation of Musicians, went on strike for two weeks three years ago and eventually agreed on a minimum salary of $43,420 a year. That contract expired in late November.