What do the values of the S9(9) field look like in hex? Do they have C signs, F signs or D signs?
What do you want the converted values to look like exactly (alphanumeric can mean a lot of things)?
You can handle the S9(9) values directly regardless of their signs by using ZD format, e.g.
OMIT COND=(27,9,ZD,EQ,666666666)
SORT FIELDS=(27,9,ZD,A)
If the values have C signs and you want them to be printable, you can use these DFSORT control statements to give the values F signs so they'll be printable:
INREC OVERLAY=(27:27,9,ZD,TO=ZDF,LENGTH=9)
OMIT COND=(27,9,CH,EQ,C'666666666')
SORT FIELDS=(27,9,CH,A)
If the values have F signs, then you don't need to convert them as they are already alphanumeric so this will work:
OMIT COND=(27,9,CH,EQ,C'666666666')
SORT FIELDS=(27,9,CH,A)
If the values have D signs, those are negative, so you have to indicate what you want the output values to look like.