hi, all, Does anyone has document/note talking about the index prefetching? I saw a few doc talking about oracle 9i introduced this feature, but no doc really talked, how it works, and how to enable/hint the prefetch for the optimizer, and how to verify it is working. I have two database with identical hardware/schema, and some SQL with identical plan (and nearly same data volume), SQL in one database always run at 1/2 time of the other database. I checked the 10046 trace and found the database faster has pretty much "db file parallel read" and the other instance is all "db file sequential read". I guess it is related to the prefetch, but do not have much detail about it. If someone has some experience it, can you share? -- Regards Zhu Chao www.cnoug.org -- //www.freelists.org/webpage/oracle-l