Nodetool compact

compact [<keyspace> <cfnames>...]- Force a (major) compaction on one or more tables. Compaction is an optimization that reduces the cost of IO and CPU over time by merging rows in the background. By default, major compaction runs on all the keyspaces and tables. Major compactions will take all the SSTables for a column family and merge them into a single large SSTable. If keyspace is provided, the compaction will run on all the tables in that keyspace. If one or more tables are provided as command-line arguments, the compaction will run on all the tables.

Examples

nodetool compact
nodetool compact keyspace1
nodetool compact standard1

Nodetool Reference