Matchcodes are used to access G/L accounts without specifying the complete account number. If you, for example, do not know the account number, you can search for the account via the G/L account text.
When defining the matchcodes, you specify which fields of a master record can be used for the search. Matchcodes are displayed from the master data tables via database indices that are possibly your own. These indices are automatically created with the matchcode definition. Since some fields of the master record, such as name or account name support upper/lower case, substitutes in upper case have been included for the matchcode queries.