In short, reason for automatic conversion is as in SAP Help stays: "As the SAP ERP planned order cannot have its own configuration, orders with CDP characteristics are created in SAP ERP as production orders."
Lets Imagine the following scenario:
In SAP ERP you create or add item to a Sales order for a configurable Material with Inhouse production. You plan in SAP APO.
When you added the new item to the Sales order there is temporary element generated in APO, also with a covering Planned order.
Also when you save the Sales order, the temporary element replaced by the the requirement of the Sales order item, and if you have the following settings, you will see that the Planned order is converted to Production order (process order) automatically:
- If the PP Planning procedure of the Product in APO, for the event 'Create or Change a Sales Order in OLTP system' it is set to 'Start Product Heuristic Immediately', and
- by sending back Planned order data to ERP: If in the customizing option 'Transfer to R/3 In-House Production' has the setting 'Always Create Transfer Events (Default)'
Since by sending Sales order data to APO you trigger the 'Create or Change a Sales Order in OLTP system' event. Also since as the help says when you send order with characteristic dependent planning back to ERP it would created as Production order, the 'Transfer to R/3 In-House Production' triggered too. To avoid this automatic conversion, you can change the setting of the customizing parameter 'Transfer to R/3 In-House Production' to 'Create Transfer Event from Conversion Indicator'. With this, you can keep your requirement in Planned order status. Also you can manually trigger the conversion by setting the Conversion indicator.
For further details you can look in online documentation for Characteristics-Dependent Planning: http://help.sap.com/saphelp_scm2007/helpdata/en/b0/b657425e060d53e10000000a155106/content.htm
The customizing setting you find in SPRO transaction here: Advanced Planning and Optimization --> Supply Chain Planning --> Production Planning and Detailed Scheduling (PP/DS) --> Global Settings --> Maintain Global Parameters and Defaults
