I have just faced a very unusual situation about creating Sourcesystems in Business Warehouse system.
Even though everything seemed to be okay, there were some tiny details that were empeding this creation. The error message RSAR501 would be issued in BW, even though the background users had all the necessary authorizations and SAP Notes 1276270 and 1081598 were already implemented by Support Package. Another symptom is the runtime error DYNPRO_SEND_IN_BACKGROUND happens in the source system during the creation.
To solve it, first check if the user maintained in the _DIALOG destination in SM59 is really dialog. If it isn’t, a dialog type user should be maintained there. You may also turn the flag “Logon Screen” on. In the screenshot below, the checkbox “Logon Screen” is already marked, but a dialog user needs to be informed.
After performing these changes, the dump DYNPRO_SEND_IN_BACKGROUND won’t happen anymore and the proper error message will be issued.
This dialog user suggestion may be a little obvious. However, there is another solution that I don’t really understand why, but somtimes works: setting Load Balancing off, as in the following screenshot: