Precedence constraints are the connections between the tasks that
control the execution order of each task. Precedence constraints are the arrows
those use in control flow pane to connect the task. It is controlling the flow of the based on a
task success fail or complete. The default
constraint is success.
The precedence constraint arrows can
be different colors to represent different commands (like success, fail,
complete etc). We can also write the expression the Constraints.
Each colour represents a status of when
a task will execute:
Ø Green = On Success
Ø Red = On Failure
Ø Blue = On Completion
Ø Any color with FX Logo =
Expression, or Expression with a Constraint
Let’s see how
to use this
Double click on the arrow. Precedence
Constraint editor will be open.
Evaluation Operation:
Constraint
When we set Evaluation operation is
Constraint then the value may be
Ø
Success: The
precedence executable must run successfully for the constrained executable to
run. This is the default value. The precedence constraint is set to green when
the Success option is selected.
Ø
Failed: The
precedence executable must fail for the constrained executable to run. The
precedence constraint is set to red when the Failure option is
selected.
Ø
Complete: The
constrained executable will run after the precedence executable runs, whether
the precedence executable runs successfully or whether it fails. The precedence
constraint is set to blue when the Completion option is selected.
If you are selecting the Logical AND
the arrow is solid.
Expression
When we set the Evaluation operation
is Expression
Expression will be enabling.
Expression is retuning Boolean values
(True or False).
When we are setting the expression the fx will be displaying on the arrow.
Expression and constraint
The precedence constraint is evaluated based on both the Value property
and the expression. Both must evaluate to true for the constrained executable
to run. I mean first task must be success and the given expression return true
then only it evaluate the true. Else it will be failed.
Expression or constraint
The precedence constraint is evaluated based
on either the Value property or the expression. At least one of these
properties must evaluate to true for the constrained executable to run.
Multiple constraints
Logical AND
All precedence constraints that point to the constrained
executable must evaluate to true in order for that executable to run. This is
the default option. If it is selected, the arrow is solid.
Logical OR
Only one precedence constraint that points to the constrained
executable must evaluate to true in order for that executable to run. If this
option is selected, the arrow is dotted
