Oracle Core # How does oracle do a data change – Redo and Undo

I am reading Jonathan Lewis’s latest book Oracle Core recently. I will note something important here.

How does oracle do a data change:

1. Create a redo change vector describing how to insert an undo record into an undo block.
2. Create a redo change vector for the data block change.
3. Combine the redo change vectors into a redo record and write it to the log buffer.
4. Insert the undo record into the undo block.
5. Change the data block.

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