Glossary

Term	Description
Cassandra	ApsaraDB for Cassandra is a reliable, online NoSQL distributed database service. It supports the SQL-like syntax CQL and multi-active deployments. It provides enterprise-level features such as security, disaster recovery, monitoring, and backup and recovery.
CQL	CQL (Cassandra Query Language) is an SQL-like query language used in Cassandra. For more information about its usage, see the Cassandra documentation.
Data center	In ApsaraDB for Cassandra, a data center (DC) is a group of nodes in the same region that are isolated by power and network. In a multi-DC deployment, service interconnection is established between DCs over the internal network. Network latency is lower within a DC, and fault isolation is provided between DCs.
partitioner	A partitioner determines the policy for distributing data evenly across nodes. In ApsaraDB for Cassandra, Murmur3Partitioner is used by default.
Number of replicas	The number of replicas specifies how many copies of data are stored in a cluster. For example, a value of 2 means that two replicas of each data row are stored in the cluster, with each replica on a different node. In ApsaraDB for Cassandra, you specify the number of replicas when you create a keyspace.
Replica policy	A replica policy determines which node stores a replica. In ApsaraDB for Cassandra, you specify the replica policy when you create a keyspace. Use the NetworkTopologyStrategy policy to more easily extend your cluster to multiple DCs.
KeySpace	A KeySpace contains one or more tables. You can specify the replica policy at the keyspace level.