> [!NOTE] ![[assets/wl_lwlock_wraplimitsvacuum.png|256]] > > | | | > | :--- | :--- | > | **Wait Category** | LWLock | > | **Mechanism** | `WrapLimitsVacuumLock` | > | **Operations** | [[Operations/Table/SeqScan]] | > | **Resources** | [[Resources/RAM|Memory]], [[Resources/CPU|CPU]] | > > Contention on the **Cluster Safety Layer**. To prevent data corruption caused by Transaction ID counter rollover, Postgres must track the "Oldest Frozen XID" and "Oldest MultiXact." If a transaction attempts to proceed past the hard limit, the cluster will automatically shut down.