> [!NOTE] ![[assets/wl_lwlock_sinvalread.png|256]] > > | | | > | :--- | :--- | > | **Wait Category** | LWLock | > | **Mechanism** | `SInvalReadLock` | > | **Operations** | [[Operations/Table/SeqScan]] | > | **Resources** | [[Resources/RAM|Memory]], [[Resources/CPU|CPU]] | > > Synchronization stall in the **Cache Consistency System**. Because every Postgres process maintains its own local cache of system catalog metadata (the Relation Cache), any change to the database structure must be communicated to every other process so they can invalidate their potentially stale local entries.