Ever wonder why your BB phone is slowing down although theres still a lot of free space?? Heres why - because BB phone has logs on whatsoever activity your doing. To clear the logs on your bb memory, simply press alt key, L, G, L, G , then the logs screen will appear, then simply delete all logs and your BB is back to normal. This is the manual procedure.
Click Options> Security Options>Advanced Security Options > Memory Cleaning> Enable> and set the time when the logs will be automatically cleared off your phone.