We use SDBILLDL in background for invoice creation. we split the jobs by customer. For 1 customer and around 1000 sales orders it is taking around 5 hrs for the job to complete. Any idea how this time can be reduced. we ran a trace and there are no custom codes having any looping issues.
1. As Yeow suggests you, SAP Note 23835 - Buffering RV_BELEG / Number assignment in SD could be so relevant.
2. Perhaps you have customer developement, but not with Z* or Y* includes. Perhaps the bottleneck is in customer VOFM. Check Note 327220 - VOFM function and its objects to identify them. Usually they begin with RV* instead LV, FV and so on. Although perhaps I am in a mistake.