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- 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 class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tutorial-install.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="tutorial-start.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="tutorial-createdb.html">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">Home</a></td><td width="40%" align="right" valign="top"> 1.3. Creating a Database</td></tr></table></div></body></html>
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