I just use this article to record my learning about BOM download.
1. In ERP, create one material 1468 "JVM":
And another material 1469 "JDK 1.8":
2. Create a BOM via tcode CS01 based on material 1468 with the following settings:
Add 1469 as line item:
Once saved, there is one entry generated in table MAST:
3. Create one download request in CRM via tcode R3AR2:
Specify MATNR to the material id of BOM header:
After I perform request download via this request, in WebUI I found that the assignment block "Components" is still empty.
The reason is the dependent material 1469 is not downloaded to CRM yet.
4. Then I first download material 1469 to CRM, and then I perform request download again via the request created in step 3.
After that in tcode SMW01 I can see necessary data for BOM structure, the relationship STRSET, is successfully downloaded.
Now go back to WebUI, I can see the expected component structure as displayed below.