<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>1.2. Architectural Fundamentals</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="tutorial-install.html" title="1.1. Installation" /><link rel="next" href="tutorial-createdb.html" title="1.3. Creating a Database" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">1.2. Architectural Fundamentals</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="tutorial-install.html" title="1.1. Installation">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="tutorial-start.html" title="Chapter 1. Getting Started">Up</a></td><th width="60%" align="center">Chapter 1. Getting Started</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="tutorial-createdb.html" title="1.3. Creating a Database">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="TUTORIAL-ARCH"><div class="titlepage"><div><div><h2 class="title" style="clear: both">1.2. Architectural Fundamentals</h2></div></div></div><p> Before we proceed, you should understand the basic <span class="productname">PostgreSQL</span> system architecture. Understanding how the parts of <span class="productname">PostgreSQL</span> interact will make this chapter somewhat clearer. </p><p> In database jargon, <span class="productname">PostgreSQL</span> uses a client/server model. A <span class="productname">PostgreSQL</span> session consists of the following cooperating processes (programs): </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> A server process, which manages the database files, accepts connections to the database from client applications, and performs database actions on behalf of the clients. The database server program is called <code class="filename">postgres</code>. <a id="id-1.4.3.3.3.3.1.1.2" class="indexterm"></a> </p></li><li class="listitem"><p> The user's client (frontend) application that wants to perform database operations. Client applications can be very diverse in nature: a client could be a text-oriented tool, a graphical application, a web server that accesses the database to display web pages, or a specialized database maintenance tool. Some client applications are supplied with the <span class="productname">PostgreSQL</span> distribution; most are developed by users. </p></li></ul></div><p> </p><p> As is typical of client/server applications, the client and the server can be on different hosts. In that case they communicate over a TCP/IP network connection. You should keep this in mind, because the files that can be accessed on a client machine might not be accessible (or might only be accessible using a different file name) on the database server machine. </p><p> The <span class="productname">PostgreSQL</span> server can handle multiple concurrent connections from clients. To achieve this it starts (<span class="quote">“<span class="quote">forks</span>”</span>) a new process for each connection. From that point on, the client and the new server process communicate without intervention by the original <code class="filename">postgres</code> process. Thus, the master server process is always running, waiting for client connections, whereas client and associated server processes come and go. (All of this is of course invisible to the user. We only mention it here for completeness.) </p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tutorial-install.html" title="1.1. Installation">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="tutorial-start.html" title="Chapter 1. Getting Started">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="tutorial-createdb.html" title="1.3. Creating a Database">Next</a></td></tr><tr><td width="40%" align="left" valign="top">1.1. Installation </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 1.3. Creating a Database</td></tr></table></div></body></html>