Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 112)

Publication 1785-UM024B-EN-P - January 2003
D-4 Program Synchronization
Should frequent program scan overruns occur, it may be necessary for
you to increase the Maximum Program Scan Time parameter. The
Maximum Program Scan Time parameter can be changed "on-the-fly"
to the primary processor while the processor is in RUN mode. Both
processors will automatically begin using the new Adjusted Maximum
Program Scan Time parameter.