> [!MessageQueueInternal] > <table><tr><td rowspan="4" width="25%"><img src="assets/wl_ipc_messagequeueinternal.png"></td><td><b>Wait Category</b></td><td>IPC</td></tr><tr><td><b>Mechanism</b></td><td><code>shm_mq</code></td></tr><tr><td><b>Operations</b></td><td><a href="Operations/Table/SeqScan">SeqScan</a>, <a href="Operations/Index/IndexScan">IndexScan</a></td></tr><tr><td><b>Resources</b></td><td><a href="Resources/RAM">Memory</a>, <a href="Resources/CPU">CPU</a></td></tr><tr><td colspan="3"><b>Parallel Resource Handshake stall</b>. To stream results back to the leader, workers must establish a connection via a "ring buffer" in shared memory.</td></tr></table>