When connecting to a servo controller with GML Commander, you need to open the correct file first. You cannot monitor logic directly as it runs as in a PLC. You can watch the lower right hand window (terminal window) to see messages generated by the controller and print blocks from the program. You can monitor system, axis, and user variables in the bottom center window. The tree view on the bottom left is where you select which category of information is displayed in the bottom center window. There are some things you can monitor directly this way, and other things (like dedicated inputs) require you to query the controller and it will report using the terminal window (bottom right).
You can't upload a GML diagram from a controller. The controller contains a script program compiled and downloaded from a GML program. It also contains setup data for each axis which is separate from the script file. It is possible to re-generate (by hand) a GML file from a script file, but it's very tedious. You have to translate the script commands individually.
If you go online using the wrong program, any changes to the user variables or axis configuration may not match. If you know that nothing like that has changed, it is okay to monitor with the wrong offline file.
To upload the program or the setups from the controller, it must be stopped first. This can be tricky depending on how it's programmed and how the RIO interface is used. Often the program will not stop on the first attempt. It is usually better to stop the program first (using the "stop program" button at the bottom) until you see Program Stopped appear in the terminal window. Then you can upload and download both script files and setup data for each axis. Then press the Go button to restart the program. It is important to understand how the PLC interacts with the 1394 controller before doing this. I have some that have the PLC programmed to start the GML program any time it isn't running. On those machines, I have to force this feature off before uploading or downloading the program in the motion controller.
It is possible (often preferred) to make logic changes without disturbing the axis setup values (gains and dynamics). In the Configure ... Control Options dialog there is a checkbox to "Download Drive/Axis Data with the Diagram". Uncheck this box to make changes to logic only when you download.
While online, if you go to Configure ... Axis Use ... <select your axis>, you get a multi-tabbed dialog that shows all the axis setup and configuration details FOR THE OFFLINE FILE. If the online file matches the offline file there will be a little checkbox on the apply page next to the controller icon (see pic).
For some reason, the software can tell this fact as soon as you're online, but it won't let you upload or download changes. If you have a match, you can adjust gains and dynamics on the fly. Just be sure to save any changes to the power up values and to the offline file. Some parameters have power-up and working values. You can make changes to the working values that are lost when you power cycle or hard reset the controller.
The status words that show global and axis faults are retentive, (except for overtravel faults) until they are reset in the program. They can be handled with an infinite variety of methods. Any logging or storage of status words is usually done in a connected PLC, but could be done with GML user variables.
Every axis fault will cause a global fault. It is common to copy each axis status word to a PLC word and log and report from there. If this hasn't been done, you can trouble shoot the system by looking at the Axis System Variables while on-line.
Select the axis in the lower left hand tree, and look at axis_status, and axis_fault variables in the bottom center window.
There's tons more ...
What specifically are you trying to do?