Understanding Tab Security
You can secure users from changing the name of the tab and viewing the form that you call by using the tab. For example, to set up change security, select the Change option. Next, drag tabs one at a time from the UnSecured node to the Secured node. The detail area reflects the changed security that you set for the tabs. This security means that the user you entered cannot change the tabs that you dragged to the Secured node.
You can define Tab security at the application, version, and form level. You cannot define Tab security at the subform level. As an alternative, you could define column security at the form level (power form level) and every instance of the data dictionary item (either on the power form header or subform grid) follows the defined security.