ALTER KEYSPACE 

Changes replication and enables or disables commit log.

Modifies the keyspace replication strategy, which is the number of copies of the data created in each datacenter, Table 2, and/or disable the commit log for writes, Durable Writes.

Restriction: Changing the keyspace name is not supported.

Synopsis 

ALTER  KEYSPACE keyspace_name 
   WITH REPLICATION = {replication_map}
   [AND DURABLE_WRITES =  true|false] ;
ALTER  KEYSPACE keyspace_name WITH REPLICATION = {replication_map} [AND DURABLE_WRITES =  true|false] ;
Legend
Syntax conventions Description
UPPERCASE Literal keyword.
Lowercase Not literal.
Italics Variable value. Replace with a user-defined value.
[] Optional. Square brackets ( [] ) surround optional command arguments. Do not type the square brackets.
( ) Group. Parentheses ( ( ) ) identify a group to choose from. Do not type the parentheses.
| Or. A vertical bar ( | ) separates alternative elements. Type any one of the elements. Do not type the vertical bar.
... Repeatable. An ellipsis ( ... ) indicates that you can repeat the syntax element as often as required.
'Literal string' Single quotation ( ' ) marks must surround literal strings in CQL statements. Use single quotation marks to preserve upper case.
{ key : value } Map collection. Braces ( { } ) enclose map collections or key value pairs. A colon separates the key and the value.
<datatype1,datatype2> Set, list, map, or tuple. Angle brackets ( < > ) enclose data types in a set, list, map, or tuple. Separate the data types with a comma.
cql_statement; End CQL statement. A semicolon ( ; ) terminates all CQL statements.
[--] Separate the command line options from the command arguments with two hyphens ( -- ). This syntax is useful when arguments might be mistaken for command line options.
' <schema> ... </schema> ' Search CQL only: Single quotation marks ( ' ) surround an entire XML schema declaration.
@xml_entity='xml_entity_type' Search CQL only: Identify the entity and literal value to overwrite the XML element in the schema and solrConfig files.
replication_map 

'class' : 'SimpleStrategy', 'replication_factor' : N

Assigns the same replication factor to the entire cluster. Use for evaluation and single datacenter test and development environments only.
REPLICATION = { 
 'class' : 'SimpleStrategy', 
 'replication_factor' : N 
}

'class' : 'NetworkTopologyStrategy', 'datacenter_name' : N, ...

After the class declaration, assign replication factors to each datacenter by name in a comma-separated list. Use in production environments and multi-DC test and development environments. Datacenter names must match the snitch DC name; see Snitches.
REPLICATION = { 
 'class' : 'NetworkTopologyStrategy', 
 'datacenter_name' : N [, 
 'datacenter_name' : N] 
 }
DURABLE_WRITES = true | false 

Optional. (Not recommended), false bypasses the commit log when writing to the keyspace. Default value is true.

CAUTION:
Never disable durable writes when using SimpleStrategy replication.

Example 

Change the cycling keyspace to NetworkTopologyStrategy in a single datacenter and turn off durable writes (not recommended). This example uses the default datacenter name with a replication factor of 3.

ALTER KEYSPACE cycling
WITH REPLICATION = { 
  'class' : 'NetworkTopologyStrategy',
  'datacenter1' : 3 } 
 AND DURABLE_WRITES = false ;