Microsoft® SQL Server 2012 Unleashed

Data Compression

Data compression, a feature available in the Enterprise and Developer Editions, helps to reduce both storage and memory requirements as the data is compressed both on disk and when brought into the SQL Server data cache.

When compression is enabled and data is written to disk, it is compressed and stored in the designated compressed format. When the data is read from disk into the buffer cache, it remains in its compressed format. This helps reduce both storage requirements and memory requirements. It also reduces I/O because more data can be stored on a data page when it’s compressed. When the data is passed to another component of SQL Server, however, the Database Engine then has to uncompress the data on the fly. In other ...