Solution : https://service.sap.com/sap/support/notes/1092157 (SAP Service marketplace login required)
Key words :
rfc destination workflow_local_<client>, required start dates, background work items, deadline monitoring processes, due dates synchronously, terms run_swwdhexrun_swwdhex_overloadwf_upg reason, swwdhex run, long runtimes, job terminations, memory overflow
Related Notes :
1125715 | Workitems fro resubmission lose current user |
1068627 | Composite note about workflow upgrade |
888279 | Regulating/distributing the workflow load |