For information about optimization hints, see "Influencing access path selection by using optimization hints" in the IBM Information Management Software for z/OS Solutions Information Center at http://publib.boulder.ibm.com/infocenter/dzichelp/v2r2/topic/com.ibm.db2z10.doc.perf/src/tpc/db2z_useoptimzationhints.htm or in chapter 41 of DB2 10 for z/OS: Managing Performance.