it may be BLOB,CLOB etc. as after deleteing some rows and running runstats,reorg ,space is not reclaimed...

The data for BLOBs and CLOBs is not stored in the same space as the regular tablespace that is associated with the table. Also, LOB's do not utilize buffer pools and are read from disk each time (unless they are LOB's associated with the DB2 catalog, in which case they may be stored in the catalog cache).