If you open a diagram in an editable state, other users cannot change that diagram until you close the diagram or release the lock. In a multi-user environment, we recommend that you open diagrams as read-only, and then lock diagrams you want to change.
1. On the Tools menu, click Options.
2. Click the Diagrams entry.
3. Select the Open Diagrams Read-only check box.
4. If you want to be warned when opening a diagram as read-only, select the Warn Before Opening Read-only Diagram check box.