A valid executable image for an alternative collation sequence must contain the following four user defined routines.

gtm_ac_xform: Transforms subscripts to the alternative collation sequence.

gtm_ac_xback: Transforms the alternative collation keys back to the original subscript representation.

gtm_ac_version: Returns a numeric version identifier for the "currently active" set of collation routines.

gtm_ac_verify: Returns the success (odd) or failure (even) in matching a collation sequence with a given version number.

Specifications for creating each of these routines are described, with examples, in the "Creating the User-defined Collation Routines" section later in this chapter.