pg_replication_slots

The pg_replication_slots view provides a listing of all replication slots that currently exist on the database cluster, along with their current state. It includes information such as slot name, type (physical or logical), associated database, activity status, and WAL positions. This view is essential for monitoring replication slot usage and ensuring proper replication behavior.

name	type	references	description
slot_name	name		A unique, cluster-wide identifier for the replication slot.
plugin	name		The base name of the shared object containing the output plugin this logical slot is using, or null for physical slots.
slot_type	text		The slot type - physical or logical.
datoid	oid	pg_database.oid	The OID of the database this slot is associated with, or null. Only logical slots have an associated database.
database	name	pg_database.datname	The name of the database this slot is associated with, or null. Only logical slots have an associated database.
temporary	boolean		True if this is a temporary replication slot. Temporary slots are not saved to disk and are automatically dropped on error or when the session has finished.
active	boolean		True if this slot is currently actively being used.
active_pid	integer		The process ID of the session using this slot if the slot is currently actively being used. NULL if inactive.
xmin	xid		The oldest transaction that this slot needs the database to retain. VACUUM cannot remove tuples deleted by any later transaction.
catalog_xmin	xid		The oldest transaction affecting the system catalogs that this slot needs the database to retain. VACUUM cannot remove catalog tuples deleted by any later transaction.
restart_lsn	pg_lsn		The address (LSN) of oldest WAL which still might be required by the consumer of this slot and thus won't be automatically removed during checkpoints. NULL if the LSN of this slot has never been reserved.
confirmed_flush_lsn	pg_lsn		The address (LSN) up to which the logical slot's consumer has confirmed receiving data. Data older than this is not available anymore. NULL for physical slots.
wal_status	text		Indicates the availability of WAL files for the replication slot. Possible values include reserved, extended, unreserved, and lost, reflecting the slot's current state regarding WAL retention.
safe_wal_size	bigint		Represents the amount of WAL data (in bytes) that can be written before the slot risks entering a lost state. A value of zero or null indicates imminent risk or that the slot is already lost.
two_phase	boolean		Indicates whether the replication slot supports decoding of prepared transactions (two-phase commit). This is true for logical slots with two-phase decoding enabled and false for physical slots.