Scalable relational systems have improvements over traditional DBMSs, to cope with performance and scalability. The following are some major scalable relational systems:

• MySQL Cluster: MySQL Cluster is a part of mainline MySQL releases, and is an extension that supports distributed, multi-master, and ACID-compliant databases.
• VoltDB: VoltDB is an open source, SQL-based, in-memory database that is designed for high performance, as well as scalability. 
• Vertica Analytics Platform: Vertica Analytics Platform is a cloud-based, column-oriented, distributed database management system.