What is SSIS validation?

SSIS validates the package and all of it's tasks to ensure it has been configured correctly. With a given set of configurations and values, all the tasks and package will execute successfully. In other words, during the validation process, SSIS checks if the source and destination locations are accessible and the meta data about the source and destination tables are stored with the package are correct, so that the task will not fail if executed. The validation process reports warnings and errors depending on the validation failure detected. For example, if the source/destination tables/columns get changed/dropped it will show as error. Whereas if you are accessing more columns than used to write to the destination object this will be flagged as a warning.