# superuser_reserved_connections

> superuser_reserved_connections is the PostgreSQL setting that defines the number of connection slots reserved for superusers.
---

> [!NOTE]
> **Fact — official short description:** “Sets the number of connection slots reserved for superusers.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `integer` | Upstream pg_settings type |
| Context | `postmaster` | Requires a server restart |
| Unit | — | Raw unit |
| Range | `0` – `262143` | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Connections and Authentication / Connection Settings | Upstream classification |
| Latest boot value | `3` | 3 |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG9.0 (research boundary) |
| Present in | PG9.0–19 Beta 3 |
| Removed in | No |
| Introduction commit | Not asserted: predates the PG9.0 research boundary |
| Commit date | — |
| Discussion | — |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0–19 Beta 3 | `3` | — | 3 |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

superuser_reserved_connections sets the number of connection slots reserved for superusers. These slots are usable only after ordinary and reserved_connections capacity is exhausted, preserving an emergency path for superusers.

superuser_reserved_connections is a POSTMASTER-context setting: PostgreSQL reads it during server startup, and a configuration reload or session SET cannot activate a new value.

reserved_connections and superuser_reserved_connections carve privileged tiers from max_connections; poolers, monitoring, replication, maintenance, and failover must all fit the same total backend budget.

## Tuning advice {#tuning-advice}

> [!TIP]
> **Advice.** These are workload-specific starting points and must be validated with measurements.

| Workload | Guidance |
| --- | --- |
| OLTP | Size superuser_reserved_connections inside max_connections from the number of independent emergency actors, pooler behavior, and failover operations. Test that ordinary saturation still leaves usable administrative access. |
| OLAP | Reserve enough slots for control, monitoring, and cancellation around heavy analytical sessions, but do not let reserves consume an excessive share of a deliberately small backend pool. |
| Small nodes | Keep superuser_reserved_connections modest relative to max_connections while preserving at least one tested emergency path; reserved slots are capacity unavailable to ordinary clients at saturation. |
{.full-width}

## Pigsty {#pigsty}

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

| Template | Effective value | Versus upstream boot | Source expression |
| --- | --- | --- | --- |
| OLTP | `10` | different | `10` |
| OLAP | `10` | different | `10` |
| CRIT | `10` | different | `10` |
| TINY | `10` | different | `10` |
{.full-width}

> [!CAUTION]
> **Advice — pending human review.** Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 = 10 (dcs); OLAP: PG9.0–19 Beta 3 = 10 (dcs); CRIT: PG9.0–19 Beta 3 = 10 (dcs); TINY: PG9.0–19 Beta 3 = 10 (dcs). Advice, pending human review — Editorial inference: Ten emergency slots preserve more operational headroom than upstream for monitoring, repair, and failover on a pooler-fronted service.

## Common pitfalls {#common-pitfalls}

- Expecting a reload or SET to activate superuser_reserved_connections, although it requires a controlled server restart.
- Counting reserved slots outside max_connections even though every tier consumes the same total ceiling.
- Reserving too little for incident response or so much that ordinary application capacity collapses at saturation.
- Changing superuser_reserved_connections globally without a rollback plan and a client or operational compatibility test.

## Related parameters {#related-parameters}

[`listen_addresses`](/parameters/listen-addresses/) · [`port`](/parameters/port/) · [`max_connections`](/parameters/max-connections/) · [`reserved_connections`](/parameters/reserved-connections/) · [`unix_socket_directories`](/parameters/unix-socket-directories/)

## References {#references}

- [PostgreSQL 19 Beta 3 — superuser_reserved_connections](https://www.postgresql.org/docs/19/runtime-config-connection.html#GUC-SUPERUSER-RESERVED-CONNECTIONS)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)