Monitoring the cluster allows you to understand what the cluster is doing at any given point in time and potentially act and react accordingly to avoid degradation in the performance and usability of databases. PostgreSQL provides a rich set of catalogs that allow a database administrator to monitor the overall activity by issuing only SQL statements and queries. You can also combine the results of the information coming from the catalog with other external monitoring tools, ranging from your operating system's tools to more complex ones such as Nagios.
In this section, we will have a look at the main PostgreSQL catalogs used to monitor and collect information about database activities. As you can imagine, only a database administrator can get complete information about overall cluster activities.
The cluster collects information about activities by means of the statistic collector, a dedicated process that is responsible for collecting, and therefore providing...