Uwe Hesse wrote:That's a really good point. Though, I think a lot of the confusion is when Oracle touts:
Keep in mind that a Smart Scan is always a Direct Read , bypassing the Buffer Cache completely.
Andy Klock wrote:These assertions are incorrect.
The statement seems to imply that Exadata has the ability to strip out columns from a block, but a block is a block is a block. Offloading is remarkable at filtering out data in the storage layer that ultimately is not needed but if you only need one row in a block that has 100 rows in it, you still get the whole block (and all 100 rows) to be processed by Oracle. The columns portion of the statement is when HCC is used for a table allowing only the blocks containing the column data required for the query, and thus if a block has 1000 column values in it, it will pass all 1000 column values to the instance to be processed.
user12064076 wrote:If i understand your question correctly, you want to know what would happen to my Select statement (containing rows/columns) if there are some modified blocks(which contain those rows/columns) in buffer cahce in case of smart scan?
Thank you all of you.
If I understand you correctly, new blocks are generated by cell server on the fly?