Oracle error 12154 while importing DMP file
Use this on Windows (three nested double quotes):

exp system/password_for_system@dev file=c:\fooadmin.dmp full=yes

imp """sys/password12345@dev as sysdba""" FROMUSER=FOOADMIN TOUSER=FOOADMIN file=c:\fooadmin.dmp


In general imp would work as intended with sys account, it is just not recommended. But exp with sys account could possibly produce inconsistent dump file silently. So it's better to avoid it, for example use system.