Page Life Expectancy (Sayfa Yaşam Süresi)

The time in seconds a database page stays resident in the buffer pool without being referenced before being flushed to free up memory.

Internal Architecture Breakdown

Page Life Expectancy is the primary canary metric for buffer pool memory pressure. The legacy 300-second threshold is obsolete for modern multi-gigabyte hosts; target PLE should scale with (Allocated Buffer Pool GB / 4) * 300.

Steep PLE cliffs indicate sudden table scans caused by missing indexes, cache churn, or unconstrained query memory grants.

Production Inspection Queries

SQL Server

SELECT object_name, counter_name, cntr_value AS ple_seconds FROM sys.dm_os_performance_counters WHERE counter_name = 'Page life expectancy';

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