Solution : https://service.sap.com/sap/support/notes/565264 (SAP Service marketplace login required)
Key words :
attached advance correction, bapi bapi_activitycrm_createmulti, terms bapi_activitycrm_createmulti, program error, 0 support package 13, 1 support package 03, performance reason, performance, bapi_activitycrm_changemulti, sufficient