PG_DATABASE

PG_DATABASE records information about available databases.

Table 1 PG_DATABASE columns

Name	Type	Description
oid	oid	Row identifier (hidden attribute, which must be specified)
datname	name	Database name
datdba	oid	Owner of the database, usually the user who created it
encoding	integer	Character encoding for the database
datcollate	name	Sequence used by the database
datctype	name	Character type used by the database
datistemplate	boolean	Whether the database can be used as a template database
datallowconn	boolean	If the value is false, no one can connect to this database. This column is used to protect the template0 database from being altered.
datconnlimit	integer	Maximum number of concurrent connections allowed on this database. The value –1 indicates no limit.
datlastsysoid	oid	Last system OID in the database
datfrozenxid	xid32	Tracks whether the database needs to be vacuumed to prevent transaction ID wraparound. This column is discarded in the current version. To ensure forward compatibility, this column is reserved. The datfrozenxid64 column is added to record the information.
dattablespace	oid	Default tablespace of the database
datcompatibility	name	Database compatibility mode. Currently, four compatibility modes are supported: A, B, C, and PG, indicating that the Oracle, MySQL, Teradata, and Postgres databases are compatible.
datacl	aclitem[]	Access permissions
datfrozenxid64	xid	Tracks whether the database needs to be vacuumed to prevent transaction ID wraparound.
datminmxid	xid	All multi-transaction IDs before this one have been replaced with a transaction ID in the database. This is used to track whether the database needs to be vacuumed in order to prevent transaction IDs wraparound (or to allow pg_clog to be shrunk). It is the minimum pg_class.relminmxid value of all tables in the database.