The following parameters set the flow control threshold levels used to determine when XON and XOFF characters need to be sent to the application.  The value of N defines the number of unused bytes in the input buffer.  If flow control is enabled, via the tandem keyword, an XOFF character is sent when the number of unused bytes in the input buffer decreases to the XOFF threshold value, and an XON character is sent when the amount of empty space in the input buffer increases to the XON threshold value.

The XON threshold value must be greater than the XOFF threshold value but no greater than the input buffer size. You should space the two thresholds far enough apart so that XON and XOFF characters do not need to be sent too often.