Use the following syntax to alter the settings of an existing cluster.
ALTER CLUSTER <cluster_name> SET
[ MIN_INSTANCES = <min_instance_count> ]
[ MAX_INSTANCES = <max_instance_count> ]
[ ALLOW_MAINTENANCE_ACCESS = { TRUE | FALSE } ]
[ COMMENT = '<comment' ]
[ INSTANCE_TYPE_FAMILY = '<instance_type_family>' ]
[ ON_DEMAND_INSTANCES = <on_demand_instance_count> ]
[ MAX_REPLAY_INSTANCES = <max_replay_instance_count> ]
[ SCALING_STRATEGY = {
LOW_COST | LOW_LATENCY | CONSISTENT_LOW_LATENCY | NO_SCALING } ]
[ STATIC_PUBLIC_IPS = <number_of_static_ips> ]
ALTER CLUSTER "My test cluster"
SET MAX_INSTANCES = 4
SET COMMENT = 'Test cluster'
SET SCALING_STRATEGY = LOW_COST;