Typo3 Install Tool Description:
Boolean: if true, data exchange between TYPO3 and database server will be compressed. This may improve performance if (1) database serever is on the different server and (2) network connection speed to database server is 100mbps or less. CPU usage will be higher if this option is used but database operations will be executed faster due to much less (up to 3 times) database network traffic. This option has no effect if MySQL server is localhost.
Bug #23346 > http://forge.typo3.org/issues/23346