When schema changes are made in Cassandra, for example by adding new tables or altering existing tables, a new schema version is generated that uniquely identifies the new schema and distinguishes it from the previous version. After a short period, Cassandra will try to propagate the schema changes to all other nodes in the cluster. During this period there may be multiple schema versions in use in a cluster. The Active Schema Versions metric shows the number of active schema versions for each node in the cluster and can help monitor schema agreement across the cluster in real time. We recommend that you wait for the schema update to finish and all nodes to report a stable schema version (i.e. a value of 1) before performing any further operations. Having multiple schema versions for a prolonged period (> 10 minutes) is unexpected and may require manual intervention. If you are experiencing issues of this nature, please contact [email protected] for help.