Hi Ganesh,
You can use following combination of services in your flow service:
1)pub.file:getFile (to get flat file from directory)
2)pub.flatFile:convertToValues (Converts a flat file to an IS document (IData object) based on the input flat file schema)
once you get the IS document then do requisite mapping with the input document of your insert adapter service.
So this way your flat file is inserted into oracle db using insert adappter service.