Equivalent in HiRDB is PCTFREE.

Oracle:

CREATE unique INDEX IX1 
     ON HANBAI_D ( mise_no DESC, shohin ASC, shohin2) 
     PCTFREE 05 
     TABLESPACE TBS_USIA_IX_10000K;

HiRDB:

CREATE unique INDEX IX1 
ON HANBAI_D 
(mise_no DESC, 
shohin ASC, 
shohin) 
     IN( TBS_USIA_IX_10000K) 
     PCTFREE=5;