# IPC: MultixactCreation

> Waiting for a multixact creation to complete
---

<div class="event-kicker">PostgreSQL wait event dossier</div>
<div class="event-identity">
  <span>Class<strong>IPC</strong></span>
  <span>Event<strong><code>MultixactCreation</code></strong></span>
  <span>Versions<strong>PG 17-18</strong></span>
  <span>Evidence<strong>1 source location(s)</strong></span>
</div>

## Official description {#official-description}

Waiting for a multixact creation to complete

| PG 13 | PG 14 | PG 15 | PG 16 | PG 17 | PG 18 |
| :---: | :---: | :---: | :---: | :---: | :---: |
| — | — | — | — | ✓ | ✓ |

## Trigger mechanism {#mechanism}

The catalog identity is present, but source audit found no live reporter in 17.8+, 18.2+. Known active ranges: 17.0-17.7, 18.0-18.1. The definition location below is retained as negative evidence; this exact release cannot emit the event from a core code path. Evidence: [PostgreSQL 17.8 release note](https://www.postgresql.org/docs/17/release-17-8.html), [PostgreSQL 18.2 release note](https://www.postgresql.org/docs/18/release-18-2.html).

## Normal or trouble? {#normal-vs-trouble}

- <span class="severity-normal">**Normal:**</span> No live core occurrence is expected on the audited release.
- <span class="severity-watch">**Investigate:**</span> If telemetry shows it, verify the exact patch version, extension origin, and whether the sample is stale or came from a different server.

## Diagnostic SQL {#diagnostic-sql}

```sql {title="Sessions waiting on IPC/MultixactCreation"}
SELECT pid, backend_type, usename, datname, application_name,
       state, now() - query_start AS query_age,
       now() - xact_start AS xact_age,
       wait_event_type, wait_event,
       pg_blocking_pids(pid) AS blocking_pids,
       left(query, 160) AS query
FROM pg_stat_activity
WHERE wait_event_type = 'IPC'
  AND wait_event = 'MultixactCreation'
ORDER BY query_age DESC NULLS LAST;
```

```sql {title="Current IPC cohort"}
SELECT wait_event, count(*) AS waiting_sessions,
       count(*) FILTER (WHERE state = 'active') AS active_waiters,
       max(now() - query_start) AS oldest_query
FROM pg_stat_activity
WHERE wait_event_type = 'IPC'
GROUP BY wait_event
ORDER BY waiting_sessions DESC, wait_event;
```

```sql {title="Lock and relation context for these sessions"}
SELECT a.pid, l.locktype, l.mode, l.granted, l.fastpath,
       d.datname, n.nspname, c.relname,
       l.page, l.tuple, l.virtualxid, l.transactionid,
       l.classid, l.objid, l.objsubid
FROM pg_stat_activity AS a
LEFT JOIN pg_locks AS l ON l.pid = a.pid
LEFT JOIN pg_database AS d ON d.oid = l.database
LEFT JOIN pg_class AS c
  ON c.oid = l.relation
 AND l.database = (
       SELECT oid FROM pg_database WHERE datname = current_database()
     )
LEFT JOIN pg_namespace AS n ON n.oid = c.relnamespace
WHERE a.wait_event_type = 'IPC'
  AND a.wait_event = 'MultixactCreation'
ORDER BY a.pid, l.granted, l.locktype, l.mode;
```

## Response {#response}

1. Identify the peer or phase named by the event.
2. Inspect that participant's wait, error, and progress state.
3. Repair the stalled participant or upstream dependency instead of treating the waiter as the root cause.

## Source evidence {#source}

- [PostgreSQL 18.6 · src/backend/utils/activity/wait_event_names.txt:143](https://github.com/postgres/postgres/blob/REL_18_6/src/backend/utils/activity/wait_event_names.txt#L143) — `MULTIXACT_CREATION`

## Related controls and signals {#related}

- **GUCs:** [[guc:autovacuum_multixact_freeze_max_age]](/guc/autovacuum-multixact-freeze-max-age/) · [[guc:vacuum_multixact_freeze_table_age]](/guc/vacuum-multixact-freeze-table-age/)
- **Metrics:** [[metric:waiting_sessions]](/metric/waiting-sessions/) · [[metric:wait_event_share]](/metric/wait-event-share/) · [[metric:oldest_multixact_age]](/metric/oldest-multixact-age/)