> [!TimelineHistoryRead] > <table><tr><td rowspan="4" width="25%"><img src="assets/wl_io_timelinehistoryread.png"></td><td><b>Wait Category</b></td><td>IO</td></tr><tr><td><b>Mechanism</b></td><td><code>Timeline</code></td></tr><tr><td><b>Operations</b></td><td><a href="Operations/Distributed/Redistribute">Redistribute</a></td></tr><tr><td><b>Resources</b></td><td><a href="Resources/disk IO">disk IO</a>, <a href="Resources/CPU">CPU</a></td></tr><tr><td colspan="3"><b>Recovery Lineage Retrieval stall</b>. Timeline history files provide the engine with the map of how the transaction log has branched over time, which is essential for determining which WAL segments to replay and in what order.</td></tr></table>