Chapter 6. Control Center

Control Center is a tool that enables you to create and manage PostgreSQL database services on a server running Red Hat Enterprise Linux 3.

Control Center enables you to access the functions provided by PostgreSQL server-side utilities such as initdb, initlocation, pg_ctl, pg_config, and pg_controldata. It also provides an alternative to the direct use of Linux system-administration utilities such as service and chkconfig.

Control Center makes it easy to browse or edit pg_hba.conf, postgresql.conf, PG_VERSION, postmaster.pid, and the backend log file. In addition, Control Center provides for the clusters it creates some of the functions that the post-installer and the RPM provide for the default cluster. Among these functions are running the regression tests and setting up the Red Hat Linux service script for a Database Cluster. The service script is used by the serviceconf, chkconfig, and service commands and also for starting the service at boot (if so configured) and stopping it at shutdown.

6.1. Terminology

Control Center operates with the following objects:

Database Clusters

Data areas that contain the catalog for all databases accessed by a database server, as well as their primary database storage area.

You must initialize Database Clusters with a Database Engine that is compatible with the Database Engine that will be used to access those Clusters. A Database Cluster can be in one of the following states:

  • Started if database client connections are currently being accepted

  • Stopped if database client connections are not being accepted

  • Not Initialized if the specified main storage area does not contain a database catalog or cannot be located in the file system.

Locations

Secondary database storage areas.

You must initialize locations with a Database Engine that is compatible with that used with the primary storage area (that is, the Database Engine used to initialize the Database Cluster).

Database Engines

Abstract representations of an installed backend program and its related utilities and files.

A Database Engine can be in one of the following states:

  • In Use if it is being used to access a Database Cluster

  • Not Used if it is not being used by a Database Cluster

  • Broken if some problem was detected (such as missing executables).

PostgreSQL Database Service

An instance of a Database Engine that listens for requests on a specific server system port and provides access to a specific Database Cluster.

Server

The physical machine on which the Database Engines and the Clusters are located. A server may have more than one cluster running on it at once, or even more than one engine.