A relational database management system (RDBMS) is a collection of programs and capabilities that enable IT teams and others to create, update, administer and otherwise interact with a relational database. Most commercial RDBMSes use Structured Query Language (SQL) to access the database, although SQL was invented after the initial development of the relational model and is not necessary for its use.
RDBMS vs. DBMS
In general, databases store sets of data that can be queried for use in other applications. A database management system supports the development, administration and use of database platforms.
An RDBMS is a type of DBMS with a row-based table structure that connects related data elements and includes functions that maintain the security, accuracy, integrity and consistency of the data.
Oracle database architecture.
Writing Sql queries.
Installing Oracle databases on Windows/Unix/Linux.