Change keyspace replication strategy

A keyspace is created with a replication strategy. For development environments, the SimpleStrategy class is acceptable. For production, you must use NetworkTopologyStrategy.

To change the strategy, alter the distribution of nodes within multiple datacenters by adding a datacenter, add data to the new nodes in the new datacenter, then finally remove nodes from the old datacenter.

Procedure

If necessary, change the snitch to a network-aware setting.
Alter the keyspace properties using the CQL ALTER KEYSPACE command.
- To change the replication strategy for the cycling keyspace from SimpleStrategy to NetworkTopologyStrategy for a single datacenter:
  ALTER KEYSPACE cycling WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy', 'DC1' : 3 };
- To change the replication strategy for the cycling keyspace from SimpleStrategy to NetworkTopologyStrategy for two datacenters:
  ALTER KEYSPACE cycling WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy', 'DC1' : 3, 'DC2' : 3 };
Simply altering the keyspace may lead to faulty data replication. Run nodetool repair with the -full option on each node affected by the change.
```
nodetool repair -full <keyspace>
```
It is possible to restrict the replication of a keyspace to selected datacenters or a single datacenter. To do this, use the NetworkTopologyStrategy and set the replication factors of the excluded datacenters to 0 (zero):
```
ALTER KEYSPACE cycling
WITH REPLICATION = {
    'class' : 'NetworkTopologyStrategy',
    'DC1' : 0,
    'DC2' : 3,
    'DC3' : 0
};
```
See Modifying the replication factor.

Change keyspace replication strategy

Procedure

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