Droid Memory Wipe

A memory wipe was a method that was used to selectively or completely erase the memory of a droid.  All databanks, except for basic factory-installed programming, were "wiped" clean. This would be  performed with a memory flush unit and was commonplace across the Galaxy.
Through their everyday experiences, droids would gradually begin to develop personality and independence, even overriding their programming. Most droid owners did not want this, so they prevented it by performing regular memory wipes. Droids tended to dread the procedure. Some evidence, however, suggested that not performing memory wipes could have beneficial effects. One such benefit was that the droid became better at inferring the wishes of its master, increasing its efficiency and accuracy. Also, droids with accumulated memories were often more effective because of their increased practical knowledge and real-world familiarity.
It was also possible to wipe the memories of shipboard computer systems. If the computer on a starship spent extended periods of time without a memory flush and spent considerable amount of time interacting with a droid a starship computer could begin to model itself after or mimic the personality of that droid. 
It has been noted that some pilots have had the memories of their astromech droids wiped after finding that in battle situations the droid's screams was too much of a distraction.