ALTER KEYSPACE

Changes keyspace replication and enable/disable commit log.

Modifies the keyspace replication strategy, the number of copies of the data Cassandra creates in each data center, REPLICATION, 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 = { 
      'class' : 'SimpleStrategy', 'replication_factor' : N  
     | 'class' : 'NetworkTopologyStrategy', 'dc1_name' : N [, ...] 
   }
   [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

Simple strategy

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

Network topology strategy

Assign replication factors to each data center in a comma separated list. Use in production environments and multi-DC test and development environments. Data center names must match the snitch DC name; refer to Snitches for more details.
REPLICATION = { 
 class' : 'NetworkTopologyStrategy', 
 'datacenter_name' : N [, 
 'datacenter_name' : N] 
 }
Note: Datacenter names are case sensitive. Verify the case of the using utility, such as dsetool status.
DURABLE_WRITES
Optionally (not recommended), bypass the commit log when writing to the keyspace by disabling durable writes (DURABLE_WRITES = false). Default value is true.
CAUTION:
Never disable durable writes when using SimpleStrategy replication.

Example

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

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