https://www.sqlserver70.com/tags/page-life-expectancy/Recent content in Page Life Expectancy on SQL Server ScriptsHugo -- gohugo.ioenSQLServer70.comSun, 06 Sep 2026 00:00:00 +0000https://www.sqlserver70.com/post/page-life-expectancy-dm-os-performance-counters/Sun, 06 Sep 2026 00:00:00 +0000https://www.sqlserver70.com/post/page-life-expectancy-dm-os-performance-counters/ <p>How many seconds should a data page sit in the buffer pool before <a href="https://learn.microsoft.com/en-us/sql/sql-server/">SQL Server</a> decides it isn't needed anymore, and where does that number actually come from? Page life expectancy is one row among hundreds returned by <a href="https://learn.microsoft.com/en-us/sql/relational-databases/system-dynamic-management-objects/sys-dm-os-performance-counters-transact-sql?view=sql-server-ver17">sys.dm_os_performance_counters</a>, and reading it correctly — along with its neighbor, buffer cache hit ratio — depends entirely on a column most ad hoc queries against this view skip past: <code>cntr_type</code>. Get that column wrong and a perfectly healthy instance can look like it's in crisis, or the reverse.</p>