Key-Compressed Indexes

Often, an index includes multiple occurrences of key column prefix values. Oracle Database's key compression feature lets you separate an index key into two entries, a prefix and a suffix. Key compression lets the suffix entries in an index block share the prefix entries, thus letting you store more keys per index block. Of course, you save on storage and you improve performance as a result. Performance may be improved since there are fewer leaf blocks that may need to be accessed due to the compression. While it's obvious that compression saves storage space, it's natural to wonder if the overhead of compression is going to negate the benefits of compressing data. In Oracle Database 11g, the new online transaction processing ...

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