前段时间，安装了个12c，无意间发现alert log里面有一些关于hugepage的信息。意思是让设置hugepage。刚开始还以为是12c的新特性。后来经过仔细研究发现，这个不是12c的特性，11g也有类似的提示。经过查看官方文档和实际测试，总结如下：
在使用AMM管理内存的时候，alert log日志中没有相关大页面的提示。
当使用ASMM管理内存的时候，alert log中有相关大页面的提示。
Starting ORACLE instance (normal)
************************ Large Pages Information *******************
Per process system memlock (soft) limit = 128 GB
Total Shared Global Region in Large Pages = 0 KB (0%)
Large Pages used by this instance: 0 (0 KB)
Large Pages unused system wide = 0 (0 KB)
Large Pages configured system wide = 0 (0 KB)
Large Page size = 2048 KB
RECOMMENDATION:
Total System Global Area size is 802 MB. For optimal performance,
prior to the next instance restart:
1. Increase the number of unused large pages by
at least 401 (page size 2048 KB, total size 802 MB) system wide to
get 100% of the System Global Area allocated with large pages
********************************************************************
LICENSE_MAX_SESSION = 0
设置hugepage后，并重启，并查看效果
Shutting down archive processes
Archiving is disabled
Sat May 26 21:39:22 2018
Instance shutdown complete
Sat May 26 22:01:57 2018
Starting ORACLE instance (normal)
************************ Large Pages Information *******************
Per process system memlock (soft) limit = 128 GB
Total Shared Global Region in Large Pages = 802 MB (100%)
Large Pages used by this instance: 401 (802 MB)
Large Pages unused system wide = 3 (6144 KB)
Large Pages configured system wide = 404 (808 MB)
Large Page size = 2048 KB
********************************************************************
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
Initial number of CPU is 1
Number of processor cores in the system is 1
Number of processor sockets in the system is 1
Picked latch-free SCN scheme 3
Autotune of undo retention is turned on.
--- 查看结果
[oracle@test trace]$ cat /proc/meminfo | grep Huge
AnonHugePages: 0 kB
HugePages_Total: 404
HugePages_Free: 136
HugePages_Rsvd: 133
HugePages_Surp: 0
Hugepagesize: 2048 kB
[oracle@test trace]$