# Cache parameter group tiers in ElastiCache
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Amazon ElastiCache has three tiers of cache parameter groups as shown following.

![\[Image: Amazon ElastiCache parameter group tiers\]](http://docs.aws.amazon.com/AmazonElastiCache/latest/dg/images/ElastiCache-ParameterGroups-Tiers.png)


*Amazon ElastiCache parameter group tiers*

**Global Default**

The top-level root parameter group for all Amazon ElastiCache customers in the region.

The global default cache parameter group:
+ Is reserved for ElastiCache and not available to the customer.

**Customer Default**

A copy of the Global Default cache parameter group which is created for the customer's use.

The Customer Default cache parameter group:
+ Is created and owned by ElastiCache.
+ Is available to the customer for use as a cache parameter group for any clusters running an engine version supported by this cache parameter group.
+ Cannot be edited by the customer.

**Customer Owned**

A copy of the Customer Default cache parameter group. A Customer Owned cache parameter group is created whenever the customer creates a cache parameter group.

The Customer Owned cache parameter group:
+ Is created and owned by the customer.
+ Can be assigned to any of the customer's compatible clusters.
+ Can be modified by the customer to create a custom cache parameter group. ‡

  ‡ Not all parameter values can be modified. For more information on Memcached values, see [Memcached specific parameters](ParameterGroups.Engine.md#ParameterGroups.Memcached). For more information on Valkey and Redis OSS values, see [Valkey and Redis OSS parameters](ParameterGroups.Engine.md#ParameterGroups.Redis).