The compression ratio achieved in a given environment depends on the nature of the data being compressed; specifically the cardinality of the data. In general, customers can expect to reduce their storage space consumption by a factor of 2 to 3 by using the OLTP Table Compression feature. That is, the amount of space consumed by uncompressed data will be two to three times larger than that of the compressed data. The benefits of OLTP Table Compression go beyond just on-disk storage savings. One significant advantage is Oracle’s ability to read compressed blocks directly without having to first uncompress the block. Therefore, there is no measurable performance degradation for accessing compressed data. In fact, in many cases performance may improve due to the reduction in I/O since Oracle will have to access fewer blocks. Furthermore, the buffer cache will be more efficiently used since it will be storing more data without having to add memory.