2026-03-12 20:23:15

timhall/monitoring/cache_hit_ratio.sql

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+-- -----------------------------------------------------------------------------------
+-- File Name    : https://oracle-base.com/dba/monitoring/cache_hit_ratio.sql
+-- Author       : Tim Hall
+-- Description  : Displays cache hit ratio for the database.
+-- Comments     : The minimum figure of 89% is often quoted, but depending on the type of system this may not be possible.
+-- Requirements : Access to the v$ views.
+-- Call Syntax  : @cache_hit_ratio
+-- Last Modified: 15/07/2000
+-- -----------------------------------------------------------------------------------
+PROMPT
+PROMPT Hit ratio should exceed 89%
+
+SELECT Sum(Decode(a.name, 'consistent gets', a.value, 0)) "Consistent Gets",
+       Sum(Decode(a.name, 'db block gets', a.value, 0)) "DB Block Gets",
+       Sum(Decode(a.name, 'physical reads', a.value, 0)) "Physical Reads",
+       Round(((Sum(Decode(a.name, 'consistent gets', a.value, 0)) +
+         Sum(Decode(a.name, 'db block gets', a.value, 0)) -
+         Sum(Decode(a.name, 'physical reads', a.value, 0))  )/
+           (Sum(Decode(a.name, 'consistent gets', a.value, 0)) +
+             Sum(Decode(a.name, 'db block gets', a.value, 0))))
+             *100,2) "Hit Ratio %"
+FROM   v$sysstat a;