Database column names in general are case sensitive on some databases, so EclipseLink is case sensitive, so you should include the correct case in your column/table names. If you database always uses upper (or lower) case, then you should do the same.
There is an EclipseLink persistence unit property that will force case to upper case on column meta-data.
"eclipselink.jdbc.uppercase-columns"="true"
There are also two methods on DatabasePlatform,
setShouldForceFieldNamesToUpperCase()
and, setShouldIgnoreCaseOnFieldComparisons() which may be useful.