Regarding when we need to use parameter reportData

Hi Experts

Could you please share me your advice on the following question

now we want to use "ScheduleService" webservice to submit the Job to BIP12c

in SOAP Request,we found the following parameter

<v2:reportData>XXXXXXXX</v2:reportData>

In the doc below,It mentioned

http://docs.oracle.com/cd/E24001_01/bi.1111/e18863/scheduleservice.htm#CACCCCBD

>>Table 2-48 Fields Provided by ReportRequest
byte[] reportData  If you are providing the data directly for the report use this element to pass the data.

But I still don't very clear on when we should input value to <v2:reportData>,and what value we should input,