The pg_database system catalog table stores information about the available databases. Databases are created with the CREATE DATABASE SQL command. Unlike most system catalogs, pg_database is shared across all databases in the system. There is only one copy of pg_database per system, not one per database.

Table 1. pg_catalog.pg_database

column type references description
datname name   Database name.
datdba oid pg_authid.oid Owner of the database, usually the user who created it.
encoding integer   Character encoding for this database. pg_encoding_to_char() can translate this number to the encoding name.
datistemplate boolean   If true then this database can be used in the TEMPLATE clause of CREATE DATABASE to create a new database as a clone of this one.
datallowconn boolean   If false then no one can connect to this database. This is used to protect the template0 database from being altered.
datconnlimit integer   Sets the maximum number of concurrent connections that can be made to this database. -1 means no limit.
datlastsysoid oid   Last system OID in the database.
datfrozenxid xid   All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this database. This is used to track whether the database needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk. It is the minimum of the per-table pg_class.relfrozenxid values.
dattablespace oid pg_tablespace.oid The default tablespace for the database. Within this database, all tables for which pg_class.reltablespace is zero will be stored in this tablespace. All non-shared system catalogs will also be there.
datconfig text[]   Session defaults for user-settable server configuration parameters.
datacl aclitem[]   Database access privileges as given by GRANT and REVOKE.