I can't delete a master page because it's being used

Issue

• I cannot delete a master page because it's being used, but we cannot find the usage.
• I have the following error message:
  • Error: You cannot delete master pages used by a page, a page template, or a display page template.

Environment

• DXP 7.3+

Resolution

• To resolve the issue, you would have to locate the source of the usage in your database.
• You can find the usage by following these steps:
  1. Search for the master page in the layout table:
     for example:
     SELECT * FROM lportal.layout where name like '%Master_Page_Name%';
  2. Based on the results locate the PLIDS that is connected to the master page in question.
  3. Search for the PLIDS in the layout table's masterLayoutPlid column
     for example:
     SELECT * FROM lportal.layout where masterLayoutPlid in (11312,11313);
  4. From the results you can find which page or page template, or display page template uses the master page in question.