Solution : https://service.sap.com/sap/support/notes/49545 (SAP Service marketplace login required)
Summary : 
      
Key words : 
additional key words deleting, private copies unlike mail, selected work items directly, archive development kit, purely administration tools, higher-level workflow, function module sww_wi_list_archived_read, single work item, work item history, archiving object workitem
Related Notes : 
       
| 887304 | MIC:FAQ, Workflow, Email, Scheduling | 
| 836092 | BPE-RUN: Archiving/deleting work items | 
| 737696 | Add. info on upgrade to SAP R/3 Enterprise 4.70 Ext. 2 SR1 | 
| 706478 | Preventing Basis tables from increasing considerably | 
| 637683 | Add info about upgrade to SAP R/3 Enterprise Core 4.70 Ext 2 | 
| 587896 | Add. info on upgrade to SAP R/3 Enterprise Core 4.70 SR1 | 
| 573656 | Collective note relating to Archiving in workflow | 
| 547893 | FAQ Workflow, definition | 
| 547601 | FAQ workflow, runtime environment and troubleshooting | 
| 420371 | Add. info on upgrading to Basis 4.6C SR2 (NDI upgrade) | 
| 390062 | Additional information about upgrading to 4.6C SR2 | 
| 329622 | Additions: Upgrading to Basis 4.6C SR1 (NDI upgrade) | 
| 327285 | Additions to upgrade to 4.6C SR1 | 
| 304597 | Additions to upgrade to Release 4.6C FCS | 
| 192949 | Additional info for upgrade to 4.6C | 
| 179373 | Additional info for upgrade to Rel.4.6B | 
| 155674 | Additions upgrade to Release 4.6A | 
| 153205 | Direct deletion of type C work items | 
| 145291 | Performance of deletion from archive file | 
| 126678 | Archiving or deleting work items of type C | 
| 98407 | Performance workflow | 
| 76431 | Measures for optimizimg the upgrade runtime 4.x | 
| 67366 | Deletion of work items is incomplete |