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

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Basic Data Change

One of the strangest features of an Oracle database is that it records your data twice. One copy of the data exists in a set of data files which hold something that is nearly the latest, up-to-date version of your data (although the newest version of some of the data will be in memory, waiting to be copied to disc); the other copy of the data exists as a set of instructions—the redo log files—telling you how to re-create the content of the data files from scratch.

images Note When talking about data and data blocks in the context of describing the internal mechanism, it is worth remembering that the word “data” generally tends to include ...

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