I don't wish to discourage you, but a true copying of sales documents with a BAPI is not fully supported as explained in note 370988 - BAPIs in SD: Creation with reference. In the same note it is described what are the possible options: 1) make an exact full copy and then adjust the result or 2) replicate in your program what copy controls do (VTAA). There is even some code example in the same note how to do this. It is for a different BAPI, but as a developer you should be able to figure out the concept and apply it to your case.
The second option mentioned there is probably closer to what you want, but speaking from personal experience, it is difficult to support such solution, because you have to adjust the code every time when customizing is changed.
As to mandatory fields and how to use them - besides the example in the note, transaction BAPI and the FM documentation provides some information how to fill the data. In addition. for filling configuration data, notes 1896387 - How to fill the configuration structure of the BAPI_SALESORDER_CHANGE and 481102 - BAPI_SALESORDER_CREATEFROMDAT2 & configuration are good starting points. There are many people who have worked on BAPI+configuration, make sure to do a Google search if you encounter problems.
Edit: Please show the results of what you read and tried when you ask for help in the future. While spec dumping is not strictly forbidden here, it decreases significantly your chances of receiving useful replies and sometimes it leads to content rejection by a moderator, because similar questions have been asked before and you forgot to explain why none of them were helpful in any way.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.