# [[metric:oldest_transaction_age]]

> Age of the oldest open transaction or visibility horizon.
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Age of the oldest open transaction or visibility horizon.

## Referenced by wait events {#wait-events}

- [Activity/AutovacuumMain](/activity/autovacuum-main/)
- [IO/LogicalSubxactRead](/io/logical-subxact-read/)
- [IO/LogicalSubxactWrite](/io/logical-subxact-write/)
- [IPC/XactGroupUpdate](/ipc/xact-group-update/)
- [LWLock/Autovacuum](/lwlock/autovacuum/)
- [LWLock/AutovacuumSchedule](/lwlock/autovacuum-schedule/)
- [LWLock/BtreeVacuum](/lwlock/btree-vacuum/)
- [LWLock/ParallelVacuumDSA](/lwlock/parallel-vacuum-dsa/)
- [LWLock/PerXactPredicateList](/lwlock/per-xact-predicate-list/)
- [LWLock/ProcArray](/lwlock/proc-array/)
- [LWLock/SerializableXactHash](/lwlock/serializable-xact-hash/)
- [LWLock/WrapLimitsVacuum](/lwlock/wrap-limits-vacuum/)
- [LWLock/XactBuffer](/lwlock/xact-buffer/)
- [LWLock/XactSLRU](/lwlock/xact-slru/)
- [LWLock/XactTruncation](/lwlock/xact-truncation/)
- [Timeout/VacuumDelay](/timeout/vacuum-delay/)
- [Timeout/VacuumTruncate](/timeout/vacuum-truncate/)