Which of the following is not a Database management system?

A Database Management System (DBMS) is software whose defining job is to store, organize, and manage persistent structured data, and to provide controlled retrieval and query access to it -- whether through SQL (relational/RDBMS) or through document/collection style APIs (non-relational/NoSQL). Any software satisfying this storage-plus-management role qualifies as a DBMS, regardless of which family it belongs to.

• MySQL is a widely used, open-source Relational Database Management System (RDBMS) -- it stores data in tables and is queried using SQL, so it is a genuine DBMS.

• MongoDB is a widely used, open-source NoSQL database management system -- it stores data as flexible, JSON-like documents, so it is a genuine DBMS even though it is not relational.

• Oracle Database is a comprehensive, multi-model enterprise Relational Database Management System (RDBMS) used widely for enterprise data management, so it is a genuine DBMS.

• Apache Spark is a distributed data-processing and analytics engine -- it computes over data (batch jobs, streaming, machine learning, graph analytics) but has no native persistent storage layer of its own, relying on an external store such as HDFS, Amazon S3, or a database to hold the data it processes. It manages computation, not data storage, so it is not a DBMS.

MySQL, MongoDB, and Oracle only differ along the RDBMS-vs-NoSQL line -- both families still store and manage persistent data, which is the core DBMS capability. Apache Spark sits in an entirely different category: a processing/compute engine rather than a data store, which is the sharper distinction the question is actually testing.

Therefore, Apache Spark is the option that is not a database management system.