The terms PostgreSQL and Postgres will be used interchangeably to refer to the software that accompanies this documentation. An administrator is generally a person who is in charge of installing and running the server. A user could be anyone who is using, or wants to use, any part of the PostgreSQL system. These terms should not be interpreted too narrowly; this documentation set does not have fixed presumptions about system administration procedures. We use /usr/local/pgsql/ as the root directory of the installation and /usr/local/pgsql/data as the directory with the database files. These directories may vary on your site, details can be derived in the Administrator's Guide. In a command synopsis, brackets ([ and ]) indicate an optional phrase or keyword. Anything in braces ({ and }) and containing vertical bars (|) indicates that you must choose one alternative. Examples will show commands executed from various accounts and programs. Commands executed from a Unix shell may be preceded with a dollar sign ($). Commands executed from particular user accounts such as root or postgres are specially flagged and explained. SQL commands may be preceded with => or will have no leading prompt, depending on the context. The notation for flagging commands is not universally consistent throughout the documentation set. Please report problems to the documentation mailing list pgsql-docs@postgresql.org.