Solution : https://service.sap.com/sap/support/notes/88168 (SAP Service marketplace login required)
Key words : 
==================================================date      topic    short description---------------------------------------------------12/mar/98 vii/ long runtimes, setenv libpath /usr/lpp/db2_05_00/lib, export libpath=/usr/lpp/db2_05_00/lib, upgrade strategy a_off04/mar/98 ii/  remark, online               documentation11/mar/98 vi/  sap db2admin, directory /db2/<sid>/log_archive/<sid>, control center11/mar/98 iv/  restarting, upgrade strategy a_off iv/ restarting, control center vi/ sap db2admin, --------------------<d024110>------------------------------------------vii/ long runtimes
Related Notes : 
       
| 91692 | Additional Info: Upgrading to 4.0A |