On our 10.2.0.3 database, we have a very simple query that is not using the index that we expected and is instead doing a full tablescan. The clustering factor of this index is very high. Have any of you encountered a similar problem? How have you solved it? Have any of you used the technique described in the book Cost-Based Oracle Fundamentals by Jonathan Lewis to adjust the clustering factor of an index using the sys_op_countchg() function? Our query is : Select * from tableA where fielda=:A and fieldb=:B We have an index on tableA (fielda, fieldb), but Oracle isn't using the index. The clustering factor of the index is : 1089825 The table is located in an ASSM type tablespace and the table stats: NUM_ROWS BLOCKS ---------- ---------- 1976721 31517 I'd appreciate your suggestions ...... or experiences using the sys_op_countchg() function. Thank you, Orysia Orysia Husak Sr. Oracle DBA - Classroom Applications Hosting University of Phoenix/ Apollo Group, Inc. Office: 602-557-6934 Mobile: 602-377-8586 orysia.husak@xxxxxxxxxxxxx