I'm reverse engineering a Database in Spring Roo. The commands database reverse engineer --schema no-schema-required (the only schema option roo shell presents me with) and database introspect --schema no-schema-required both return the message

Schema(s) 'no-schema-required' do not exist or does not have any tables. Note that the schema names of some databases are case-sensitive

But when I run database reverse engineer --schema dbo or database introspect --schema dbo I get the expected results. What does DBO stand for / do in this instance?