The storage engine of OceanBase Database uses the log-structured merge-tree (LSM tree) architecture. In this architecture, data is stored in a MemTable and an SSTable. When the memory occupied by the MemTable exceeds the specified threshold, data in the MemTable is flushed to the SSTable to release the memory space. This process is called a minor compaction. A minor compaction generates a new SSTable. When the number of minor compactions exceeds the specified threshold, or during off-peak hours, the system merges the baseline SSTable with the incremental SSTables generated by minor compactions into one SSTable. This process is called a major compaction.
For more information about minor compactions, see Minor compactions.
For more information about major compactions, see Major compactions.