Solution : https://service.sap.com/sap/support/notes/1084132 (SAP Service marketplace login required)
Key words :
enter archive information structure workitem, archive information structure sap_bo_2_wi_001, archive information structure sap_o_2_wi_001, archive information structure, workitem archiving object, prerequisites - solution proceed, call transaction sari, select infostructure sap_bo_2_wi_001, select infostructure sap_o_2_wi_001, choose 'delete structures'
Related Notes :
| 1086814 | RSWWARCP does not determine archived workflows |
| 573656 | Collective note relating to Archiving in workflow |