What is rds parameter group in AWS?
*You can manage your DB engine configuration through the use of parameters in a DB parameter group.
*DB parameter groups act as a container for engine configuration values that are applied to one or more DB instances.
*A default DB parameter group is created if you create a DB instance without specifying a customer-created DB parameter group.
*This default group contains database engine defaults and Amazon RDS system defaults based on the engine, compute class, and allocated storage of the instance.
*You cannot modify the parameter settings of a default DB parameter group.
*Simply we can say DB engine related configurations and values will be saved here . Based on this your values DB engine will function.
*In traditional servers we can have access to underlying Operating system , but in RDS you cant get access to OS.
*So you can fine tune data base engine parameters value based on this parameter group settings.
*you must create your own DB parameter group to change parameter settings from their default value. Note that not all DB engine parameters can be changed in a customer-created DB parameter group.
*When you change a dynamic parameter and save the DB parameter group, the change is applied immediately regardless of the Apply Immediately setting. When you change a static parameter and save the DB parameter group, the parameter change will take effect after you manually reboot the DB instance.
*For more information
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_WorkingWithParamGroups.html