Parameters for PostgreSQL Cluster

This page lists the parameters that can be customized through a DB Configuration Group when using vDB PostgreSQL Cluster (1 Writer + N Readers).

• These parameters apply to PostgreSQL versions 15, 16, 17.

• Restart Required = Yes: Changing this parameter requires a restart of the cluster to take effect.

• Restart Required = No: Changes are applied immediately without a restart.

• All parameters in the list are modifiable.

Memory note: Many parameters directly affect total RAM consumed by PostgreSQL. Setting values too high relative to the node's RAM can cause PostgreSQL to be OOMKilled.

Parameters that affect memory:

• max_connections — when active queries are running, memory increases due to work_mem allocated per sort/hash operation, multiplied by the number of concurrent connections

• shared_buffers — allocates shared memory at PostgreSQL start and does not return it to the OS for the lifetime of the process; setting it too large squeezes the OS page cache and reduces I/O efficiency

• work_mem — multiplied by the number of concurrent connections and the number of sort/hash operations per query; total actual usage can be very large when many complex queries run in parallel

• temp_buffers — temp table buffer per session, multiplied by max_connections

• max_worker_processes — each background worker consumes additional memory

• max_wal_senders — each WAL sender process requires additional memory

Choose values appropriate for the RAM of the node flavour in use.

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Connections

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
max_connections	100	25 - 2000	integer		Maximum number of concurrent connections to the database	Yes

Memory & Buffers

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
shared_buffers	16384	16 - 1073741823	integer	8kB	Memory used as a shared buffer between backend processes	Yes
work_mem	4096	64 - 2147483647	integer	kB	Memory for ORDER BY, JOIN, DISTINCT; uses disk when exceeded	No
maintenance_work_mem	65536	1024 - 2147483647	integer	kB	Memory for VACUUM, CREATE INDEX	No
temp_buffers	1024	100 - 1073741823	integer	8kB	Buffer memory per session	No
max_prepared_transactions	0	0 - 262143	integer		Number of transactions in prepared state	Yes

Autovacuum

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
autovacuum	on	true / false	boolean		Enable/disable Autovacuum	No
autovacuum_naptime	60	1 - 2147483	integer	s	Time between two vacuum runs on the same table	No
autovacuum_vacuum_threshold	50	0 - 2147483647	integer		Row update/delete threshold to trigger VACUUM	No
autovacuum_analyze_threshold	50	0 - 2147483647	integer		Row change threshold to trigger ANALYZE	No

Logging

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
log_min_duration_statement	-1	-1 - 2147483647	integer	ms	Log queries that run longer than the specified duration. Value -1 = disabled	No

Query Planning & Optimization

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
effective_cache_size	524288	1 - 2147483647	integer	8kB	Estimated disk cache for the planner to choose indexes	No
random_page_cost	4	0 - 1.79769e+308	float		Cost of random page access	No
seq_page_cost	1	0 - 1.79769e+308	float		Cost of sequential page access	No
enable_seqscan	on	true / false	boolean		Enable/disable sequential scan	No
enable_indexscan	on	true / false	boolean		Enable/disable index scan	No
enable_hashjoin	on	true / false	boolean		Enable/disable hash join	No

Locale & Format

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
DateStyle	ISO, MDY	See table below	string		Date/time display format	No

Supported DateStyle values:

DateStyle	Input Example	Output Example
ISO, DMY	01-02-2026 → 1 Feb 2026	2026-02-01
ISO, MDY	01-02-2026 → 2 Jan 2026	2026-01-02
ISO, YMD	2026-02-01 → 1 Feb 2026	2026-02-01
SQL, DMY	01-02-2026 → 1 Feb 2026	01/02/2026
SQL, MDY	01-02-2026 → 2 Jan 2026	01/02/2026
SQL, YMD	2026-02-01 → 1 Feb 2026	2026-02-01
Postgres, DMY	01-02-2026 → 1 Feb 2026	Fri 01 Feb 00:00:00 2026
Postgres, MDY	01-02-2026 → 2 Jan 2026	Fri 02 Jan 00:00:00 2026
Postgres, YMD	2026-02-01 → 1 Feb 2026	Fri 01 Feb 00:00:00 2026
German, DMY	01.02.2026 → 1 Feb 2026	01.02.2026
German, MDY	01.02.2026 → 2 Jan 2026	02.01.2026
German, YMD	2026.02.01 → 1 Feb 2026	01.02.2026

Asynchronous & Workers

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
max_worker_processes	32	2 - 65536	integer		Maximum number of background worker processes	Yes

Replication & WAL

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
wal_level	replica	replica / logical	string		Level of information written to WAL. Set to logical to use Logical Replication or CDC	Yes
max_wal_senders	10	10 - 65536	integer		Maximum number of WAL sender processes, used for streaming replication and CDC	Yes
max_wal_size	2048	32 - 2147483647	integer	MB	Maximum WAL size before triggering a checkpoint	No
checkpoint_timeout	300	30 - 86400	integer	s	Maximum time between two automatic checkpoints	No

Transactions & Locking

Parameter	Default Value	Allowed Values	Type	Unit	Description	Restart Required
max_locks_per_transaction	64	10 - 2147483647	integer		Maximum number of locks per transaction	Yes