Title: How to freeze MR/IR/SR once they move to a downstream operation (PO, GRN, Issue, Appointment, Service Order)?

@RuwanK the workflow is the built-in tool for this. Access rights won't do it on their own, because they're set per role, not per document status. They can hide Cancel from a role in every status, but not only once a PO exists.

If MR, IR and SR are request classes on the Requests screen (RQ301000), one workflow covers all three. The Requests workflow is a single flow for every class, so a condition on the Request Class is how you'd treat one class differently.

The automatic reopen is part of that predefined workflow. From 2025 R1 through 2026 R1, a Closed request moves back to Open by itself whenever its open quantity goes up again. That's a transition in the workflow, not a preference. Purchase Requisitions Preferences (RQ101000) has no setting for it.

The lever is a customization project. Extend the system workflow for Requests, then work state by state. On the Fields tab you can mark a field such as the quantity Disabled, and that setting can come from a condition when the status doesn't change at the PO step. On the Actions tab you switch off Cancel by clearing Active. A canceled request comes back through Put On Hold, so clearing Active on that action in the Canceled state blocks it. System actions can't be deleted, only deactivated. I haven't tested removing the Closed to Open transition, so try that part in a test tenant first.