The engine configuration settings that are applied to one or more DB instances are contained in DB parameter groups.
Only Multi-AZ DB clusters are covered by DB cluster parameter groups. The parameters in the DB cluster parameter group are applied to all of the DB instances in a Multi-AZ DB cluster. Each DB instance in the DB cluster uses the default DB parameter group for the DB engine and DB engine version.
A default DB parameter group is used when a DB instance is created without a DB parameter group being specified. Similar to the previous example, a default DB cluster parameter group is used when a Multi-AZ DB cluster is created without a DB cluster parameter group being specified.
In accordance with the instance’s engine, compute class, and allotted storage, each default parameter group contains database engine defaults and Amazon RDS system settings. A default parameter group’s parameter settings cannot be changed. As an alternative, you create your own parameter group (refer to the below screenshot) and select your own parameter settings.
Note that In a parameter group, you define, not all DB engine settings can be altered.
Big Data and SQL 
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