two indexes with same columns = problem

Hi, Ifx 11.50 FC9X6 AIX 6.1 We have a table where two columns are used for filter : create table tst ( col1 int , col2 int); select * from tst where co1 = 9 and col2 = 350 Today exists an index over this two cols: create index i1 on tst ( col2,col1); For a specific SQL this index is used but will be more efficient if the cols appear in reversed order; Suggested index: create index i2 on tst ( col1, col2 ); Reason: if I execute this counts: select count(*), 'col1' from tst where col1 = 9 union all select count(*), 'col2' from tst where col2 = 350 the output is something like 15 'col1' 1800 'col2' If I just create the second index, the engine still usinging the i1 . If I drop both, and create i2 first and i1 after...then the engine use i2 ... So... when have 2 indexes with the same columns, the engine use the index what was created first. I look at documentation and found nothing... anyone know if have some explanation or is a defect? Regards Cesar