From the 10053 it appears that the different NDV calculation for histograms in 10.2.0.4 may be root cause for the flip from NLJ to HJ when changing OFE. If you put these two files in a graphical diff tool, it makes it fairly obvious. Look at the Single Table Cardinality Estimation section. OFE=10.2.0.4 Column (#11): PRTY_ID(NUMBER) AvgLen: 4.00 NDV: 232607 Nulls: 1694696 Density: 4.0792e-06 Min: 1 Max: 1591999 Histogram: HtBal #Bkts: 254 UncompBkts: 254 EndPtVals: 247 Using density: 4.0792e-06 of col #11 as selectivity of unpopular value pred Table: LETTER_BIN Alias: LETTER_BIN Card: Original: 4739017 Rounded: 12 Computed: 12.42 Non Adjusted: 12.42 OFE=10.1.0 Column (#11): PRTY_ID(NUMBER) AvgLen: 4.00 NDV: 232607 Nulls: 1694696 Density: 4.8136e-04 Min: 1 Max: 1591999 Histogram: Freq #Bkts: 247 UncompBkts: 254 EndPtVals: 247 Table: LETTER_BIN Alias: LETTER_BIN Card: Original: 4739017 Rounded: 1465 Computed: 1465.41 Non Adjusted: 1465.41 What is the difference in execution time of the two queries in allstats_both_queries.txt ? This may be one of those edge cases that is best dealt with by using either a hint or an outline. -- Regards, Greg Rahn http://structureddata.org -- //www.freelists.org/webpage/oracle-l