SET FILTER TO ... >>>LOCATE>>
GO TOP and LOCATE (FOR .T.) uses a ordered by TAGNO() scan* exists a index TAGUSEDFOROPTIMIZATION for the filter condition
GO TOP use a ordered by TAGNO() scan FOR condition uses a full optimized SEEK ( time is o(Log(RECCOUNT))2 TAGNO()#TAGUSEDFOROPTIMIZATION
GO TOP use a ordered by TAGNO() scan FOR condition uses a partial optimization ( time is o(RECCOUNT))3 TAGNO()=TAGUSEDFOROPTIMIZATION
GO TOP use a ordered by TAGNO() scan FOR condition uses a partial optimization when it can uses a full optimization. Sin.The workaroud is SET KEY.