Questions You Asked: Why do I sometimes get better compression using Advanced Row compression compared to In-Memory Query compression?
By Vineet Marwah-Oracle on Jun 03, 2016
The compression techniques that are use for in-memory compression are different from what we use for on-disk compression. The compression on-disk is designed to reduce the overall space usage for the table segments. While the compression algorithms used in memory are designed for query performance and speeding up the queries by being able to operate on the compressed format. Due to the different techniques, it is not uncommon to have table segments see different compression ratios and different sizes in-memory and on-disk.[Read More]