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Oracle Core: Essential Internals for DBAs and Developers by Jonathan Lewis

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C H A P T E R  2

Redo and Undo

The Answer to Recovery, Read Consistency, and Nearly Everything—Really!

In a conference session I call “The Beginners’ Guide to Becoming an Oracle Expert,” I usually start by asking the audience which bit of Oracle technology is the most important bit and when did it first appear. The answers I get tend to go through the newer, more exciting features such as ref partitioning, logical standby, or even Exadata, but in my opinion the single most important feature of Oracle is one that first appeared in version 6: the change vector, a mechanism for describing changes to data blocks, the heart of redo and undo.

This is the technology that keeps your data safe, minimizes conflict between readers and writers, and allows ...

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