I am currently pending I-485 (EB3, skilled worker employment based, priority date Oct 2008) since April 2014. I submitted inquiries through congressman, they received a letter that my case is on hold indefinitely. Do you recommend filing Writ of Mandamus or would that cause a denial? What other actions can I take, I've submitted a case through the Ombudsman and met with a USCIS officer through Infopass appointment (who told me nothing). No RFEs have been issued for this case, I-140 was approved and fingerprinting done (twice, since first set expired).
See clip from Attorney Rajiv S. Khanna's conference call video that addresses this question.