The present invention provides a computer-implemented method, computer system and computer program product for data compression. According to the computer-implemented method, one or more data blocks on a data source to be replicated to a data target may be detected. Then, compression performance of a first compression dictionary may be evaluated. The first compression dictionary may be previously used to compress existing data on the data target. If the compression performance is lower than a preset performance threshold, a second compression dictionary may be generated based on the existing data on the data target. The data target may be updated based on the existing data and the one or more data blocks using the second compression dictionary.