This operation triggers the rewriting of SSTables that are not running on the current Cassandra version, which also ensures compatibility of SSTable with running versions of Cassandra. This is generally used during upgrade processes. It has some limitations, such as version 2.0.x of Cassandra cannot directly upgrade to 3.11.x. Therefore 2.0.x has to be first upgraded to 2.1.x, and then the 3.11.x version. Moreover, it has to be done across all the nodes to make it consistent across the cluster:
$CASSANDRA_HOME/bin/nodetool upgradeSSTable
