What is the scope of command stsadm -o migrateuser

I have multiple web applications on SP 2007 Farm. Many user accounts are common on both web applications user info list. When i run stsadm -o command to migrate user from one AD domain to another AD domain. it only migrates users in one web application. The same account on another web application did not migrated, I want to know what is the scope of stsadm -o command? is it migrate users on web application level or Farm level? During running stsadm -o migrateuser command, i did not specify any web application

please advise and correct my understanding?