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3.6. pg_database

The pg_database catalog stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult the Administrator's Guide for details about the meaning of some of the parameters.

Unlike most system catalogs, pg_database is shared across all databases of a cluster: there is only one copy of pg_database per cluster, not one per database.

Table 3-6. pg_database Columns

Name Type References Description
datname name   Database name
datdba int4 pg_shadow.usesysid Owner of the database, initially who created it
encoding int4   Character/multibyte encoding for this database
datistemplate bool   If true then this database can be used in the "TEMPLATE" clause of CREATE DATABASE to create the new database as a clone of this one.
datallowconn bool   If false then no one can connect to this database. This is used to protect the template0 database from being altered.
datlastsysoid oid   Last system OID in the database; useful particularly to pg_dump
datvacuumxid xid   All tuples inserted or deleted by transaction IDs before this one have been marked as known committed or known aborted in this database. This is used to determine when commit-log space can be recycled.
datfrozenxid xid   All tuples inserted by transaction IDs before this one have been relabeled with a permanent ("frozen") transaction ID in this database. This is useful to check whether a database must be vacuumed soon to avoid transaction ID wraparound problems.
datpath text   If the database is stored at an alternative location then this records the location. It's either an environment variable name or an absolute path, depending how it was entered.