Setting Precedence Constraints on Tasks and Containers
After a package contains multiple tasks or containers, you can link them into a sequenced workflow using precedence constraints. Each precedence constraint references two executables: two tasks, two containers, or one of each. They are known as the precedence executable and the constrained executable. The precedence executable is the task or container whose execution outcome (success or failure) can determine whether the next task or container, the constrained executable, runs. For more information, see Precedence Constraints.
In a linear control flow, that is, one without branching, precedence constraints alone govern the sequence in which tasks run. If a control flow branches, the Integration Services run-time engine determines the execution order among the tasks and containers that immediately follow the branching.
The run-time engine also determines execution order among unconnected workflows in a control flow.
The default precedence constraint uses a constraint only, and the constraint requires that the precedence executable runs successfully. Precedence constraints can be modified to use expressions with constraints or to use expressions instead of constraints, and to specify that the precedence executable fails or merely completes.
SSIS Designer uses color to identify the type of precedence constraint. The Success constraint is green, the Failure constraint is red, and the Completion constraint is blue. To display text labels in SSIS designer that show the type of the constraint, you must configure the accessibility features of SSIS Designer. For more information, see Accessibility in Business Intelligence Development Studio.
After you create a default precedence constraint, you can modify the properties of the precedence constraint.
To create a default precedence constraint
To modify a precedence constraint
Adding Functionality to Precedence Constraints
After you create a default precedence constraint, you can extend the precedence constraint in the following ways:
- Add expressions to the constraint. For more information, see Adding Expressions to Precedence Constraints.
- Configure the constraint to be evaluated in combination with other constraints. For more information, see Applying Multiple Precedence Constraints.