we did a delta load of the BSEG (SAP FICO) based on FiscalYear Period this was stored as a table in SAP BW on DSO/ODS level. We wrote a separate QVD per FYP. The complete (INITIAL) load lasted approx. 30 hours (253 mlj records) and per FYP this was approx. 1 hour..... The requestnumber is more logical but this was not available in the table we had available at that time. Whatever field you use make sure it is indexed because otherwise the load will take lots of time because of the WHERE clause you have to use in the SQL statement of the load.
dd you get any further regards the topic in the meantime ? i think it's not really possible to automate delta processes. even in sap bw you have to start and initiate the process manually. the only automation aspect i see is using variables in the case you're extractong data from sap erp using time stamps or any kind of incremental key.
hope this helps !
from our side, we have worked on the new SAP Extractor Connector (5.6) in order to get incremental load from our BW system.
At the moment, only one cube has been roll out and even if performances are very good, it is not so simple to implement.
Moreover, second roll out on a more complex cube showed bad performance.