Description

   Call SOR$DTYPE to define a key data type not normally supported
   by SORT/MERGE.

   If your SORT/MERGE application needs to compare dates (for
   example) that are stored in text form and that is the only key
   in the records, then use the user_compare argument to SOR$BEGIN_
   SORT or SOR$BEGIN_MERGE. However, if the records contain several
   keys besides the dates in text form, it may be easier to call
   SOR$DTYPE to allocate a key data type code that can then be used
   in the the key_buffer argument to SOR$BEGIN_SORT or SOR$BEGIN_
   MERGE.

   If your SORT/MERGE application has a string key that should be
   collated by a collating sequence defined by the NCS utility, the
   NCS$GET_CS routine can be used to fetch the collating sequence
   definition, and SOR$DTYPE can be called to allocate a key data
   type code for the collating sequence. This key data type code
   can then be used to describe keys that should be compared by this
   collating sequence.