To learn which changes are restricted, review the following information:

Restrictions

• If you change the class of the data page, the new class must inherit from the original class of the data page. This restriction applies if you overwrote a data page in the previous application, and then overwrote it in another application before upgrading.

  For example, you overwrite a data page that was originally part of the Customer class and changed the class to the Customer-Data class, which inherits from the Customer class. When you overwrite the data page again, you must choose a class that inherits from the Customer-Data class.

• Do not change the structure of the data page, for example, from a Page structure to a List structure.
• If the data page has parameters, do not make the following changes:
  • Change the type of parameter
  • Add new required parameters
  • Remove parameters
• If the scope of your data page is Node, do not change the scope.
• The following restrictions apply to changing the mode of a data page:

  Mode	Change to Read-only allowed	Change to Editable allowed	Change to Savable allowed
  Read-only		✔	✔
  Editable	X		✔
  Savable	X	X

Unit testing

Unit testing is crucial for making sure that the data page behaves as expected after you make changes to it. For more information, see Unit testing a data page and Testing Pega applications.