The CXO-Master Database is a relational database that contains some system metadata across all applications within the CXO installation.
It contains global features and links on CXO applications. Every CXO installation has one Master Database. You might need to change the Master Database if the SQL server has been moved to a different location. When you choose Change master database command, CXO Installation Wizard will be opened:
The Master database is defined within the Master DataBase Connection within the Configurator Application