[otrs] Help Required

Hi All… I am a new OTRS user…I am confused with the meanings of LOCK and CLOSE tickets. What they imply ??? Secondary, I want that if a ticket is unsolved by some agent for 3 days, an notification mail b delivered directly to the higher authorities. How can I do that Thanks all….. No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.8/906 - Release Date: 7/17/2007 6:30 PM