image: "assets/wl_io_wal_summarywrite.png" description: "Waiting for a write to a WAL summary file." publish: "true" status: "hardened" --- > [!WalSummaryWrite] > <table><tr><td rowspan="4" width="25%"><img src="assets/wl_io_wal_summarywrite.png"></td><td><b>Wait Category</b></td><td>IO</td></tr><tr><td><b>Mechanism</b></td><td><code>WALSummarizer</code></td><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>Incremental Backup Metadata Persistence stall</b>. The WAL Summarizer continuously scans the WAL stream and generates small "summary" files that track block-level changes.</td></tr></table>