After the File adapter writes a line to a file, the adapter sends a LineWritten event. See the com.apama.file package in the API Reference for EPL (ApamaDoc) for detailed information on the LineWritten event.

This is useful when you want your application to send FileLine events in a batch to control flow. If you need to do flow control, you would typically set all the requestIds to positive values and emit the next FileLine events only after receiving the LineWritten notification for the previous FileLine event you sent. If you do not need to do flow control, you could set requestId=-1 for all but the last FileLine event, but set it to a positive value for the very last FileLine event so you get a single LineWritten notification when everything has been written.

The file remains open for the lifetime of the adapter unless you emit a CloseFile event. See also Opening files for reading.