The catalog pg_database stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult Chapter 18 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.
Owner of the database, usually the user who created it
encoding
int4
Character encoding for this database
datistemplate
bool
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
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 rows 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 rows 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 wrap-around 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.
datconfig
text[]
Session defaults for run-time configuration variables
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