Translations:PostgreSQL/QuickStart/12/en

The PostgreSQL ebuilds in Portage feature slotting based on the major version. This allows you to have two major versions of PostgreSQL operating simultaneously; 8.4 and 9.0 libraries and servers can be installed and serve at the same time. This is useful in such circumstances where you need to move data from an older database to a new database, or need to have a production and a testing database on the same machine. Also, this prevents a database, corresponding libraries or executables from being overwritten by an incompatible update. That would require migration which is described in this guide.