Solution : https://service.sap.com/sap/support/notes/1132422 (SAP Service marketplace login required)
Key words : 
unnecessary long runtimes occured, rebuild oft11 implementation entries, t12 definition entries, dead lock situation, terms enh_build_cross_for_enhsaprupgm reason, t03 enhcross rebuild, t06 enhcross rebuild, created enhcross entries, create table entries, table entries created
Related Notes : 
       
| 1138351 | Long runtime of background job SAPRUPGM | 
| 954792 | Known problems with Support Packages in SAP NW 7.1 AS ABAP | 
| 822379 | Known problems with Support Packages in SAP NW 7.0x AS ABAP |