Host Synchronization Error

Applies to:  Foxtrot LE

Summary

Foxtrot scripts cannot be run at full speed or generate error message ("Host synchronization…", "Check screen failed…") when connected to a Unisys host system.

Cause

Unisys uses extensive buffering to maximize throughput to the emulator screen.  The result of this strategy is that the emulator screen may not reflect the current status of the host system – and may differ from the status codes returned from the host.  While these differences are not noticeable to a human operator, they can result in errors when Foxtrot runs scripts at full speed.

Resolution

Foxtrot provides specific support for the Unisys environment, which accommodates contradictions between host status and screens. This support is provided through: a) the Unisys Enter option, and b) Retry Check Screen and Retry Script Search.

UNIISYS ENTER: The Unisys Enter option is located under "Tools/Preferences/Timing & Running" in Foxtrot 2000 or "Tools/Options/Preferences/Unisys Enter" in Foxtrot Enterprise.  Check this option to allow Foxtrot to determine the host’s "ready" status by screen status instead of host return codes.  The "Try up to X Seconds" setting allows you to set the upper limit for Foxtrot to wait for the host screens to stop changing after a "transmit/enter" or other Control Key that changes the screen.

RETRY CHECK SCREEN AND RETRY SCRIPT SEARCH: The "Unisys Enter" option is located under "Tools/Preferences/Scripting" in Foxtrot 2000 or "Tools/Options/Preferences/Scripting" in Foxtrot Enterprise.  These options allow Foxtrot to retry Script Search and Check Screens for the amount of time identified in the "Try up to X Seconds" setting, testing only at intervals determined by the "Try every X Seconds" setting.  Optionally, both these Control Keys have a "Wait for Redraw Only" option which uses the same timing options to determine if the host screens have stopped changing then execute their respective functions (Check Screen or Script Search) only once.  The "Wait for Redraw Only" is substantially quicker and usually adequate for Unisys environments.

For best performance in a Unisys environment, we recommend using the "Unisys Enter" option with a 5-8 second setting.  You will need to determine the lowest setting that works for your system by trial and error.  If you still receive occasional errors while running scripts at full speed, you may need to use the "Retry" options fine-tune Foxtrot’s operations.  Here, too, you will need to determine the optimal setting for "Try up to..." and "Try every…" through trial and error.

Please see the Foxtrot documentation for more information on Unisys Enter, Retry Check Screen and Retry Script Search.