Disclosed is a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with the Internet of Things (IoT), and may be applied to intelligent services based on 5G and the IoT-related technologies, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method herein by a terminal in a communication system includes receiving a radio resource control (RRC) message including information associated with a change from a first packet data convergence protocol (PDCP) entity for a bearer to a second PDCP entity for the bearer, identifying first data to be transferred from the first PDCP entity to the second PDCP entity among second data stored in the first PDCP entity, transferring the first data to the second PDCP entity, discarding the second data stored in the first PDCP entity and releasing the first PDCP entity, and processing the transferred first data in the second PDCP entity.