Operator glossary
Terms used consistently across identity, analysis, advice, and evidence fields.
| Term | Meaning in this atlas |
|---|---|
| Active foreground session | A client-facing backend with state = 'active'; background main loops are excluded from contention percentages. |
| Snapshot share | The fraction of sampled active foreground sessions on one event. It is a triage signal, not elapsed-time attribution. |
| Wait identity | Exact (wait_event_type, wait_event) spelling observed in a release. Renames remain separate matrix rows. |
| Canonical event | One semantic dossier that can consolidate explicitly verified historical spellings or type moves. |
| Trigger | The source path that passes a wait-event identifier to PostgreSQL’s wait reporting machinery. |
| Catalog definition | A source row that defines the public name/description. It is not automatically proof of a live trigger. |
| Dormant event | A catalog identity with verified negative source evidence: no live core reporter in the audited patch release. |
| Heavyweight lock | SQL-visible lock-manager object, normally diagnosable through pg_locks and pg_blocking_pids(). |
| LWLock / tranche | Short internal lock protecting shared-memory state; the tranche supplies the displayed event name. |
| SLRU | Small shared cache and on-disk segment set for transaction-related metadata such as pg_xact and multixact. |
| Buffer pin | A backend’s temporary claim that a shared buffer page must remain present and structurally stable. |
| Source release | Exact audited tag, such as REL_18_6; line numbers are never attached to a drifting stable branch. |
Advice thresholds in this site are operational defaults. PostgreSQL does not promise that “10%” or “five seconds” is universally bad; use the cluster’s own baseline and service objectives.