The Designer has three communication modes that affect data flow to and from the Gateway:
| • | Off: All database query traffic and tag subscriptions and writes will be blocked. |
| • | Read-Only: tag subscriptions and SELECT queries will work, but tag writes and UPDATE/INSERT/DELETE queries will be blocked. |
| • | Read/Write: All data will be passed through to the Gateway. |
The mode can be switched at any time via the tri-state toggle selection in the main toolbar, or the radio buttons in the Project menu. The Designer starts up in Read-Only mode as a safety mechanism, so that you don't inadvertently write to a tag as you are designing. You can customize the designer's startup mode, see the Designer General Properties section.
A common beginner mistake is to forget to switch the mode to Read/Write when attempting to test a window's functionality in preview mode. |
 A component with the GW_COMM_OFF quality overlay |
Experts often use the Off mode while designing a window to temporarily shut off data flow so that they can manipulate components' bound properties without the values being overwritten by the data bindings. This is useful to set the values that they want to serialize into the window. This can be important for windows with large datasets; clearing the datasets before saving the window can significantly reduce the size of the window, improving performance.
Note: This setting does not affect the execution of a project's transaction groups. This is because transaction groups execute on the Gateway, not in the Designer.