Note that Dmitry's answer and mine are pretty much the same, except that I like to avoid post conditional commands where it´s not strictly needed 
Hi Sebastian,
Set FF = ""
For {
Set FF=$Order(^Users(FF))
If FF="" Quit
If $Get(^Users(FF,"SETTINGS","isAllowed"))=1 {
Write !,"User ",FF," is allowed"
}
}
Rgds
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Hi Rizmaan,
If you are using System Management Portal to run it, you need to select "ODBC Mode".
Rgds