Hi.
Automatic Memory Management (AMM) doesn't support HugePages. As a result,
you have potential for wasting lots of memory on page tables.
https://oracle-base.com/articles/linux/configuring-huge-pages-for-oracle-on-linux-64
In contrast, Automatic Shared Memory Management (ASMM) does support
HugePages.
The DBCA has some guidance for this decision process. From the 12.2
documentation:
https://docs.oracle.com/en/database/oracle/oracle-database/12.2/admin/managing-memory.html#GUID-04EFED7D-D1F1-43C3-B78F-0FF9AFAC02B0
"Oracle recommends automatic memory management for databases where the
total size of the SGA and PGA memory is less than or equal to four
gigabytes."
"If you create your database with Database Configuration Assistant (DBCA)
and choose the basic installation option, automatic memory management is
enabled when system memory is less than or equal to 4 gigabytes. When
system memory is greater than 4 gigabytes, automatic memory management is
disabled, and automatic shared memory management is enabled. If you choose
advanced installation, then DBCA enables you to select automatic memory
management or automatic shared memory management."
Rules of thumb are always lies, but I never use AMM. ;)
Note. I guess there may be differences of opinions on some operating
systems, but if it's not Linux, I'm not interested. :)
Cheers
Tim...
On Thu, Jan 23, 2020 at 5:39 PM ahmed.fikri@xxxxxxxxxxx <
ahmed.fikri@xxxxxxxxxxx> wrote:
Hi,
Coincidentally, I have seen in a productive DB that it is used AMM instead
of Asmm. I'm a developer with a bit of a dba knowledge. Our software uses a
huge db and does complex calculations.
In my experience, using amm we had only problems with other customers on
11g and 12c
In addition, I have read many articles, that recommend to use asmm instead
of amm.
The DBA is ready to use Asmm, but only if I convince him.
The question: It is true that amm is not good (huge db, lot of sessions,
parallels work)
If I'm right how can I connvince the dba?
Thanks
Ahmed
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