Deadlock issue in Purchase Order Approvals

Since we migrated to 11510, we have been facing locking issue during PO Approval. The workflow always errored out with table PO_HEADERS_ALL locking issue. We have had the same customizations in 1159 and 11510.

What changed in 11510 is that all updates to PO_HEADERS_ALL table are moved to autonomous session. And our custom code did not have this change. Once we changed our custom updates to be done in autonomous session, this issue was gone for good.

How did I find out the issue?

I checked through core PO code, and saw that all the updates to PO_HEADERS_ALL are done in autonomous session. Checked that on metalink too, found Note 749923.1 and Note 404774.1 which point to core code updates not being in autonomous mode leading to deadlocks. This was good enough indicator to move the custom updates to PO_HEADERS_ALL in autonomous session.