Renewal erased a being's memory. The term was used by the Syndicat and the people of Phindar to describe a process of memory wiping that they used as a cruel means of punishment.
As a young JediPadawan, Obi-Wan Kenobi was subjected to renewing, However he was able to keep his memory intact through the use of his Force abilities. It was said among the Phindians that some strong-minded beings could resist being renewed.
It was also a process the Ssi-ruuvi used to cleansed a human brain of any resistance before the implementation of new thoughts and ideas.