VTAM® uses buffer pools to control the handling of data. It dynamically allocates and deallocates space in buffer pools for the VTAM control blocks, I/O buffers, and channel programs that control the transmission of data. Specifying large buffer pools can waste storage, but does not require frequent CPU use for expansion. Specifying small buffer pools conserves storage, but requires frequent CPU use for expansion and contraction. With proper tuning, you can achieve a balance between storage use and performance that is suitable for your environment.