Do you have an index on itm_numb ?
If you have SET ANSI OFF, then you should be able to just use:
SELECT itm_numb,itm_desc FROM A WHERE itm_numb='STI'
which should take advantage of the index which you should then be able to confirm with the SYS(3054, command.
By using SUBSTR(itm_numb,3) you're not allowing RUSHMORE to optimize unless you specifically have an index on SUBSTR(itm_numb,3)
Brandon Harker
Sebae Data Solutions