系統：rhel 7.3
數據庫 :Oracle 12.2.0.1.0

APPLIES TO:
Oracle Database Configuration Assistant - Version 11.2.0.3 to 12.2.0.1 [Release 11.2 to 12.2]
Linux x86-64
***Checked for relevance on 18-Apr-2017***
SYMPTOMS
On Linux, create database with DBCA on systems with more than 4 GB physical memory ignores memory_target and does not set up AMM in 11.2.0.3 or higher version.

This is visible when the database is created in silent mode from a template, ASMM will be set even if memory_target >0. 

In interactive mode you may mark AMM at the corresponding step - it will not be marked by default.

Note: In database 12.2, you could encounter DBT-11211 when use AMM on OS whose memory > 4GB. You have to make use of ASMM instead of AMM.

CAUSE
In response to unpublished
Bug 12540053 : USE SGA_TARGET WHEN THE SYSTEM HAS MORE THAN 4G OF MEMORY

DBCA will setup sga_target and not memory_target when the system has more than 4GB of physical memory.

SOLUTION
This change was intended and was implemented to simplify the starting point/seed database across platforms, so that huge/large pages can be used if configured.

On platforms such as Linux there are huge pages limitations in using memory_target that do not affect all platforms.

The use of AMM is absolutely incompatible with huge pages on Linux. AMM overwrites huge pages.
 

DBT-11211 when use AMM on OS whose memory > 4GB