This question is probably not an ODS or Base Reporting procedure (PRINT, REPORT, TABULATE) question.
Generally, speaking, a column or field called "FLAG" is meant to signal some condition. Usually in a program. Imagine that I use the file SASHELP.CLASS and I want to answer some question (do any names start with 'A'). I might have this:
if substr(name,1,1) = 'A' then flag = 'y';
proc print data=countA;
where flag = 'y';
Of course this is a silly example, because there are other ways to print a list of students whose names start with 'A'. But the point is that the use of FLAG as a variable or field is specific to the kind of program that FLAG appears in. There is an instance, where an SQL procedure view will create a column called "FLAGS" -- (and a few other places) as described here: http://support.sas.com/kb/19/578.html http://support.sas.com/kb/5/346.html
But you did not say this question was related to SQL or PROC CONTENTS.
Your best bet for help with this question is to contact SAS Technical Support. To send a question to Tech Support, go to http://support.sas.com/ and in the left-hand navigation pane, click on the link entitled "Submit a Problem".