Structure of DBMS

DBMS means Database Management System, which is a tool or software used to create the database or delete, or manipulate the database.

Query Processor, Storage Manager, and Disk Storage are the three parts that make up the database system.

The explanations for these are provided below:

1. Query Processor:

The query processing is handled by the query processor, as the name implies. It executes the user's query, to put it simply. In this way, the query processor aids the database system in making data access simple and easy. The query processor's primary duty is to successfully execute the query. The Query Processor transforms (or interprets) the user's application program-provided requests into instructions that a computer can understand.

There are the following components of the query processor:

DDL Interpreter:

Data Definition Language is what DDL stands for. As implied by the name, the DDL Interpreter interprets DDL statements like those used in schema definitions (such as create, remove, etc.). This interpretation yields a set of tables that include the meta-data  (data of data) that is kept in the data dictionary. Metadata may be stored in a data dictionary. In essence, it is a part of the disc storage that will be covered in a later section of this article.

DML compiler:

Compiler for DML Data Manipulation Language is what DML stands for. In keeping with its name, the DML Compiler converts DML statements like select, update, and delete into low-level instructions or simply machine-readable object code, to enable execution. The optimization of queries is another function of the DML compiler. Since a single question can typically be translated into a number of evaluation plans. As a result, some optimization is needed to select the evaluation plan with the lowest cost out of all the options. This process, known as query optimization, is exclusively carried out by the DML compiler. Simply put, query optimization determines the most effective technique to carry out a query.

Embedded DML pre compiler:

Before the query evaluation, the embedded DML commands in the application program (such as SELECT, FROM, etc., in SQL) must be pre-compiled into standard procedural calls (program instructions that the host language can understand). Therefore, the DML statements which are embedded in an application program must be converted into routine calls by the Embedded DML Pre-compiler.

Query Optimizer:

It starts by taking the evaluation plan for the question, runs it, and then returns the result. Simply said, the query evaluation engine evaluates the SQL commands used to access the database's contents before returning the result of the query. In a nutshell, it is in charge of analyzing the queries and running the object code that the DML Compiler produces. Apache Drill, Presto, and other Query Evaluation Engines are a few examples.

2. Storage Manager:

An application called Storage Manager acts as a conduit between the queries made and the data kept in the database. Another name for it is Database Control System. By applying the restrictions and running the DCL instructions, it keeps the database's consistency and integrity. It is in charge of retrieving, storing, updating, and removing data from the database.

Components of storage manager:

Integrity manager:

Whenever there is any change in the database, the Integrity manager will manage the integrity constraints.

Authorization manager:

Authorization manager verifies the user that he is valid and authenticated for the specific query or request.

File Manager:

All the files and data structure of the database are managed by this component.

Transaction Manager:

It is responsible for making the database consistent before and after the transactions. Concurrent processes are generally controlled by this component.

Buffer Manager:

The transfer of data between primary and main memory and managing the cache memory is done by the buffer manager.

3. Disk Storage:

There are the following components of disk storage:

Data Dictionary:

It contains the metadata (data of data), which means each object of the database has some information about its structure. So it creates a repository which contains the details about the structure of the database object.

Data Files:

This component stores the data in the files.

Indices:

These indices are used to access and retrieve the data in a very fast and efficient way.