> [!VersionFileSync] > <table><tr><td rowspan="4" width="25%"><img src="assets/wl_io_versionfilesync.png"></td><td><b>Wait Category</b></td><td>IO</td></tr><tr><td><b>Mechanism</b></td><td><code>PG_VERSION</code></td></tr><tr><td><b>Operations</b></td><td><a href="Operations/Table/SeqScan">SeqScan</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>Database Identity Durability Barrier</b>. The <code>PG_VERSION</code> file is a fundamental safety check that prevents a Postgres engine from accidentally attempting to open a data directory created by a different (and potentially incompatible) major version of the software.</td></tr></table>