Parameter management - Amazon ElastiCache for Redis
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Parameter management

Parameters are grouped together into named parameter groups for easier parameter management. A parameter group represents a combination of specific values for the parameters that are passed to the engine software during startup. These values determine how the engine processes on each node behave at runtime. The parameter values on a specific parameter group apply to all nodes that are associated with the group, regardless of which cluster they belong to.

To fine-tune your cluster's performance, you can modify some parameter values or change the cluster's parameter group.

  • You cannot modify or delete the default parameter groups. If you need custom parameter values, you must create a custom parameter group.

  • The parameter group family and the cluster you're assigning it to must be compatible. For example, if your cluster is running Redis version 3.2.10, you can only use parameter groups, default or custom, from the Redis3.2 family.

  • If you change a cluster's parameter group, the values for any conditionally modifiable parameter must be the same in both the current and new parameter groups.

  • When you change a cluster's parameters, the change is applied to the cluster either immediately or, with the exceptions noted following, after the cluster nodes are rebooted. This is true whether you change the cluster's parameter group itself or a parameter value within the cluster's parameter group. To determine when a particular parameter change is applied, see the Changes Take Effect column in the tables for Redis-specific parameters.

    For more information, see Rebooting nodes.

    Redis (Cluster Mode Enabled) parameter changes

    If you make changes to the following parameters on a Redis (cluster mode enabled) cluster, follow the ensuing steps.

    • activerehashing

    • databases

    1. Create a manual backup of your cluster. See Making manual backups.

    2. Delete the Redis (cluster mode enabled) cluster. See Deleting a cluster.

    3. Restore the cluster using the altered parameter group and backup to seed the new cluster. See Restoring from a backup with optional cluster resizing.

    Changes to other parameters do not require this.

  • You can associate parameter groups with Redis global datastores. Global datastores are a collection of one or more clusters that span Amazon Regions. In this case, the parameter group is shared by all clusters that make up the global datastore. Any modifications to the parameter group of the primary cluster are replicated to all remaining clusters in the global datastore. For more information, see Replication across Amazon Regions using global datastores.

    You can check if a parameter group is part of a global datastore by looking in these locations:

    • On the ElastiCache console on the Parameter Groups page, the yes/no Global attribute

    • The yes/no IsGlobal property of the CacheParameterGroup API operation