Hello List! During our last meetup meeting in Sydney (http://www.sydneyoracle.com.au) a discussion on Exadata solution triggered a question: How read consistency is ensured during Smart Scan Offload processing? Does Oracle reconstruct consistent image of a block on Database Cell or on Storage cell? Form my understanding it should be done on DB server side as Undo data might not be available from the storage host (unless some Magic involved :). On the other hand Oracle's white papers suggest that storage sells returns relative rows and columns only. If it true is it possible to reconstruct a consistent image of the data than? Note: The Exadata consistency read question might become even more interesting if to think about "Smart Scan Join Processing". Alex Gorbachev suggested that Exadata Offload processing might be similar to the way Direct path reads are processed in a regular Oracle Database. It seams like a reasonable suggestion. The Full Scan Offload Processing should look something like the following: --- Step A. on DB server: Issue "object checkpoint" against the table we are going to scan --- Step B. on Storage cell: Reads and filter rows from data blocks that are consistent with SQL SCN. Send those to DB server. --- Step C. on Storage cell: All block with SCN higher than SQL SCN are sent to DB server to make those consistent and filter those there --- Step D. Reconstruct a consistent version of data blocks returned in step C and filter those --- Step E. Return result set to a client session is it close to the way Exadata smart scan works, what do you think? I would really appreciate any input from the list members, Thank you in advance, Yury -- //www.freelists.org/webpage/oracle-l