Abstract: Relational database is the key information infrastructure of today’s society. The Internet and digitization have brought high concurrency and massive data. Due to their centralized architectures, the processing power and storage capacity of traditional relational databases are stretched. OceanBase is a distributed relational database based on commodity PC servers. It achieves online horizontal scalability, automatic lossless disaster recovery from data center failure and high-ratio data compression. It has been used in finance, government affairs, telecommunication systems, Internet, etc. We introduce the architecture and some key technologies of OceanBase, including distributed transaction processing, LSM-tree-based storage system and distributed SQL optimizer. In addition, we explain in detail the high availability and data consistency of OceanBase, which can ensure that RPO is 0 and RTO is less than 8 seconds. At the same time, it also introduces OceanBase’s multi-tenant mechanism, which adopts a native multi-tenant design within the cluster to implement multiple independent database services in the cluster. Based on the Sysbench and TPC-H evaluation benchmarks, comparative experimental results show that 1) in a stand-alone mode, the performance of OceanBase is 1.27 times to over 2 times that of MySQL; 2) in a single-master mode, the performance of OceanBase is 1.25 times to nearly 2 times that of MySQL; 3) in a multi-master mode, the performance of OceanBase is 1.09 to 3.1 times that of MySQL, and for complex OLAP queries, the performance of OceanBase is 6 to 327 times that of MySQL.