Config file in SSIS is used to provide inputs to connection manager different properties that package use to assign values at runtime dynamically.
Using config file users need to make changes to the config file which package will take automatically at runtime because of using it you don’t need to every time make changes in the packages every in case you are deploying package on multiple servers or locations. There are multiple ways in which configuration values can be stored.
XML configuration file : Store the config file as an XML file.
* Environment variable Store the config in one of the environment variables.
* Registry entry Store the config in the registry
* Parent package variable Store the config as a variable in the package that contains the tasks.
* SQL Server Store the config in a table in SQL Server
