In this book, the author provides only the most necessary information about the internal device of the Oracle DBMS, which every database administrator must know in order to successfully deal with problems. From the outside, Oracle looks complicated. In fact, extensive functionality is based on a very small basic infrastructure, which is the result of architectural solutions taken at the very beginning and have passed the test of time. The publication is intended for database administrators who are ready to improve their skills when DBMS management is carried out on the basis of deep knowledge and understanding of the features of its work.