Database Engine

The job of the database engine is distributed between a handful of components

Storage Manager

The storage manager provides an interface that connects low-level data inside the database, to application programs that submit queries to the DBMS

The storage manager is responsible for: * Exchanging data with the OS file manager * Efficient storage, retrieval, and updation of data * Effective implementation of data files, data dictionary, and used indices

Query Processor

The query processor parses and translates the query given to the DBMS. It converts it to a relational algebra expression, which is passed to the processing engine

Transaction Manager

A logical function is broken down into a collection of operations. The result of this function is returned by performing these operations and combining their results. This collection of operations is referred to as a Transaction. The component responsible for regulating transations is called the Transaction Manager

It also maintains the database's consistency in case of a system failure (power failure / OS crash) or a transaction failure

Concurrency-Control Manager

The concurrency-control manager ensures that concurrent transactions don't lead to race conditions, and thus preserves the consistency of the database