When you create an environment variable, you can define some special behavior that takes effect when the variable is assigned to a project. Use this behavior to make your environment variable groups more flexible, creating groups with some variables which are ignored, read-only, required, or hidden when the group is assigned to a project.
To use the special behavior, set the On Project property when you create or edit an environment variable.
The On Project property offers the following options:
Normal: The variable behaves normally when assigned to a project.
Required: The system prompts for a value for the variable if no default value is defined.
Read-Only: The value of the variable cannot be changed when the group is assigned to a project.
Suppress Display: The variable is not displayed on the project Start page, although the value still exists and can be used in steps.
Must Change: You must change the variable's value when you launch the project; if you do not, the system prompts you to change it.