This topic explores the relationships among log streams, partitions, and replicas.
A log stream is a sequence of consecutively increasing log data that records all changes in the database. These changes are fundamental for synchronizing all data, as replicas, primary and standby databases, and backup data all rely on the change information captured in the logs.
In OceanBase Database V4.x, physical change records are aggregated into well-organized log streams: one system log stream and multiple user log streams. All physical change information is recorded in these log streams, and this set of physical change information is used for fault recovery, log archiving, standby database synchronization.
Within a tenant, a log stream can have multiple replicas. These replicas synchronize data with each other by using the Paxos protocol, enabling a recovery point objective (RPO) of 0 and a recovery time objective (RTO) of less than 8s when the minority of replicas fail.
In OceanBase Database V4.x, partitions are a logical concept to users, serving as a mechanism to divide and manage table data.