Solution : https://service.sap.com/sap/support/notes/1494665 (SAP Service marketplace login required)
Summary : 
      When data transfer processes (DTP) for real-time data acquisition (RDA) are used in SAP, a delay over 60 seconds in generating new DTP requests is observed. This occurs when the system verifies previously loaded delta requests in the Persistent Staging Area (PSA), slowing significantly with numerous undeleted requests. Errors such as RS_EXCEPTION 240 and RS_EXCEPTION 120 happen during this delay. The solutions involve importing specific Support Packages for various versions of SAP NetWeaver BW. In urgent cases, advance corrections with reference to Note 875986 and transaction SNOTE are advisable.
Key words : 
real-time data acquisition, solution sap netweaver bw 7, sap netweaver bw 7, sap nw bw 7, persistent staging area, sapbinews nw bi 7, data transfer process, rda daemon requires, 01 bw abap sp08, message number rs_exception 240
Related Notes : 
       
| 1471463 | SAPBWNews NW BW 7.01 ABAP SP08 | 
| 1468668 | SAPBWNews NW7.0 BW ABAP Support Package 25 | 
| 1450990 | SAPBWNews NW BW 7.02 ABAP SP05 | 
| 1392433 | SAPBINews NW7.11 BW ABAP Support Package 05 |