<Para>

A single <Application>postmaster</Application> manages a given collection of

databases on a single host. Such a collection of

databases is calledan installation or site. Frontend

databases is calleda cluster (of databases). Frontend

applications that wish to access a given database

withinan installation make calls to the library.

withina cluster make calls to the library.

The library sends user requests over the network to the

<Application>postmaster</Application>

(<XRef LinkEnd="PGARCH-CONNECTIONS" EndTerm="PGARCH-CONNECTIONS">(a)),

<Para>

A single <Application>postmaster</Application> manages a given collection of

databases on a single host. Such a collection of

databases is calledan installation or site. Frontend

databases is calleda cluster (of databases). Frontend

applications that wish to access a given database

withinan installation make calls to the library.

withina cluster make calls to the library.

The library sends user requests over the network to the

<Application>postmaster</Application> (<XRef LinkEnd="ARCH-CLIENTSERVER" EndTerm="ARCH-CLIENTSERVER">),

which in turn starts a new backend server process

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<sect1 id="terminology">

<title>Terminology</title>

<para>

In the following documentation,

<firstterm>site</firstterm>

may be interpreted as the host machine on which

<Productname>Postgres</Productname> is installed.

Since it is possible to install more than one set of

<Productname>Postgres</Productname>

databases on a single host, this term more precisely denotes any

particular set of installed

<Productname>Postgres</Productname> binaries and databases.

</para>

<para>

The

<Productname>Postgres</Productname> <firstterm>superuser</firstterm>

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<chapter id="query">

are <firstterm>attributes</firstterm>.

As previously discussed, classes are grouped into

databases, and a collection of databases managed by a

single <application>postmaster</application> process constitutesan installation

or site.

single <application>postmaster</application> process constitutesa

database cluster.

</para>

</sect1>