SSIS-Precedence Constraints

The green arrow represents On Success and means that the second (or downstream) task will only execute if the first (or upstream) task or set of tasks executes successfully.

-- The green arrow indicates that when the previous task is successful, execute the task.

The blue arrow represents On Completion and means that regardless of whether the upstream task completes successfully or fails, the downstream task will execute. This is useful for a clean-up task, for example.

-- The blue arrow indicates that after the previous task is completed, the next task is executed no matter whether the task is successful or fails.

The red arrow represents On Failure and means that the downstream task will execute only if the upstream task fails.

-- The red arrow indicates that when the previous Task fails, a certain step is executed.

You can also place expressions on the precedence constraint. with this functionality, you can put code on the constraint that states that the expressions must be true, and optionally the constraint must be true as well. these are useful if you
Want to add conditions into your control flow.

-- Adds control conditions to the control flow.