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Buffer Cache Not Fully Allocated Immediately If DB_CACHE_SIZE Is Greater Than 100GB (Doc ID 2390125.1)

Last updated on AUGUST 04, 2018

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 and later
Oracle Solaris on SPARC (64-bit)

Symptoms

With manual memory management on 12.1.0.2, setting db_cache_size greater than 100GB, however allocated buffer cache didn't honor the setting after starting the database: only 72GB memory allocated for buffer cache at the beginning. And after one month (or less time), the buffer cache size eventually honors the setting (increased to more than 100GB).

The problem seems only seen when setting db_cache_size greater than 100GB (setting it to 80GB cannot recreate the problem).

Setting hide parameter '_memory_imm_mode_without_autosga'= FALSE can't help.

 

For db_cache_size= 110G, total sga = 120G

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Changes

With manual memory management on 12.1.0.2, setting db_cache_size greater than 100GB

Cause

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