When connecting to a managed system through a direct serial connection, Operations Sentinel uses software flow control. This software can command the managed system to stop sending data until Operations Sentinel is ready to read and process more data, which helps avoid losing data because of data overruns. This works only if the console port of the managed system is configured properly. Normally, software flow control is enabled.

Operations Sentinel uses the standard START and STOP control characters to implement its flow control. When Operations Sentinel begins reading data from the managed system it sends a STOP character to command the system to stop sending data. The STOP character is DC3 (Ctrl-S, hex 13).Once the serial port manager has finished reading and processing the outstanding data, it sends a START character. This tells the managed system to send more data. The START character is DC1 (Ctrl-Q, hex 11).

To be sure your console port is configured properly, use the following command:

stty ixon -ixoff start ^q stop ^s < /dev/console

This stty command operates on its standard input (/dev/console) and can perform the following actions: