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

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Database Writer Interactions

The database writer doesn’t operate in a vacuum, and given its intent to protect the data “eventually” some time after the log writer has copied the log buffer to disk, it won’t come as a surprise to learn that dbwr has to co-operate with other processes on the system. We’ll start our examination of how dbwr behaves by looking at its interaction with lgwr, and then we’ll move on to the way it has to share the LRU lists with other processes, and take a close look at the checkpointing mechanism that aims to copy a steady stream of dirty buffers to disk.

Database Writer Meets Log Writer

Lgwr always writes changes before dbwr writes data blocks. This means a data block that’s on disk can always be moved “to the future” ...

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