Solution : https://service.sap.com/sap/support/notes/1026396 (SAP Service marketplace login required)
Key words : 
monitor table col_usage$, solution oracle bug 5709414, procedure dbms_stats, time-consuming, terms dbms_stats, mon_mods$ reason, called automatically, deleting lines, merge patch 6340979, dbms_stats package
Related Notes : 
       
| 948197 | Merge fix for DBMS_STATS package on Oracle 9.2.x and 10.2.x |