Don't expect they can be so efficient. They made some mistake on my file before, name mis-match and wrong address, I send letter and went to local office, still did not fix it. It almost caused me trouble when I came back from visiting China at the US port by holding I131. The port officer could not find my file in the DB. Finally we got to talk to the director at the local office and got it fixed. Because my wrong address which I requested change by letter and office visit but still not corrected in their DB, the first interview letter was returned without my awareness. My whole PR process was delayed more than 1 year!
Talking about government bureaucracy!