CHAPTER 16

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Hybrid Columnar Compression

Exadata Hybrid Columnar Compression, or HCC, is a type of segment compression first made available by Oracle on the Exadata Database Machine. HCC is designed to provide the highest levels of database segment compression.

With HCC, data is organized for storage by columns. Oracle uses the concept of a “compression unit” (CU) with HCC, which stores data by columns but only for a set of rows—this collection of groups of rows organized and compressed together is what leads to the “hybrid” tag in the feature name.

HCC offers very high compression ratios for QUERY compression and even higher compression ratios ...

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