The $XABKEY macro allocates and initializes a XABKEY. No value is
    returned for this assembly-time operation.

    Format

      $XABKEY  COLTBL=collating-table-address,

               DAN=data-bucket-area-number,

               DFL=data-bucket-fill-size,

               DTP={BN2|DBN2|BN4|DBN4|BN8|DBN8|IN2

               |DIN2|IN4|DIN4|IN8|DIN8|COL|DCOL |PAC|DPAC|STG|DSTG},

               FLG=<CHG DAT_NCMPR DUP IDX_NCMPR KEY_NCMPR NUL>,

               IAN=index-bucket-area-number,

               IFL=index-bucket-file-size,

               KNM=key-name-buffer-address,

               LAN=lowest-level-index-area-number,

               NUL=null-key-value,

               NXT=next-xab-address,

               POS=<position,...>,

               PROLOG=prolog-level,

               REF=key-of-reference-value,

               SIZ=<size,...>