Why not use Redo log for consistent read
Oracle 11.1.0.7:
This might be a stupid question.
As I understand if a select was issued at 7:00 AM and the data that select is going to read has changed at 7:10 AM even then Oracle will return the data that existed at 7:00 AM. And for this Oracle needs the data in Undo segments.
My question is since redo also has past and current information why can't redo logs be used to retreive that information? Why is undo required when redo already has all that information.