Actions only have access to files which are selected in the main window when the action starts. While an action can be marked in the Action Manager as All Files, this will preselect all files before the action starts.
There might be times when you want to process the metadata of those files you have selected and then expand the scope of the execution to include all visible loaded files (ie. not hidden). This statement will do just that.
When any of the following conditions are met, the statement is ignored and the action test state is set to false, otherwise the action test state is set to true.
You can restore the set of initial files by executing a Restore Initial Set of Files statement.
Additional information can be found in the File Availability topic.