Confusion about Redo Log Buffer and Undo Segments
Hi,
I have 2 questions that I have doubts about.
1> What exactly does Redo Log Buffer contains ? Does it contain before image of an updated row too ?
2> When an instance is shut down does the Undo Segments in the Undo Tablespaces get flushed ?
Suppose I am updating a row and in the middle of updating the instance goes down while I have not commited the update statement. Then when the instance comes up how Oracle will Roll Forward the row to its previous value ? Will it access Undo Segments in the Undo Tablespace ? Please clear my doubts as I am just entering the field of Oracle DBA from DWH field.
Thnaks in advance.