Global Data will allow you to save private data key(s), dataset(s), or all information from a job (including private data, and datasets) in the Switch database.
Once set in any Global Data element, you can get multiple Global Data at once, anywhere else in Switch at any moment with another Global Data element regardless if it's the same job or not.
Want to see all Global Data available? List them in a dataset.
Do not need a specific set of Global Data anymore? Simply delete them.
The primary use is to enable a developing concept known as an "Environment variable".
An "Environment variable" is generally used to save passwords, key, IP address, Folder path, available press list, email address, and so on...
With Global Data, when such value needs an update no need to change them manually everywhere in the flow. Change them once, and it's set globally.
A good practice is to use a specific flow to set global data in conjunction with Submit Point, or Switch Client, no need to open the Switch Designer for everyday changes.
We believe that a lot of other possibilities are possible with Global Data:
List available press at a given time;
Last email address used for customer BAT;
Temporary email template (holidays, Christmas, …);
Stock/Restore job information when a job goes out for another software and come back;