修改时间 15-SEP-2011 类型 BULLETIN 状态 PUBLISHED | |||
In this Document
Purpose
Scope and Application
HugePages and Oracle Database 11g Automatic Memory Management (AMM) on Linux
References
Applies to:
Oracle Server - Enterprise Edition - Version: 11.1.0.6 and later [Release: 11.1 and later ]Linux OS - Version: 2.6 and later ]
Linux x86
IBM: Linux on System z
IBM: Linux on POWER Systems
IBM S/390 Based Linux (31-bit)
Linux x86-64
Linux Itanium
Purpose
This document discusses the interoperability of the Automatic Memory Management (AMM) feature introduced by Oracle Database 11g and the HugePages (HugeTLB) feature of the Linux OS kernel.Scope and Application
This document is to be used by Linux system administrators and Oracle database administrators that work with Oracle Database Server 11g on Linux Operating System.HugePages and Oracle Database 11g Automatic Memory Management (AMM) on Linux
The 11g AMM feature is enabled by the MEMORY_TARGET / MEMORY_MAX_TARGET instance initialization parameters (see Document 460506.1 for further information). That is also the case with a default database instance created using Database Configuration Assistant (DBCA).With AMM all SGA memory is allocated by creating files under /dev/shm. When Oracle DB does SGA allocations that way HugePages are not reserved/used. The use of AMM is absolutely incompatible with HugePages.
Please also note that ramfs (instead of tmpfs mount over /dev/shm) is not supported for AMM at all. With AMM the Oracle database needs to grow and reduce the size of SGA dynamically. This is not possible with ramfs where it possible and supported with tmpfs (which is the default for the OS installation).
If you want to use HugePages make sure that both MEMORY_TARGET / MEMORY_MAX_TARGET initialization parameters are unset (i.e. using "ALTER SYSTEM RESET") for the database instance.(See also Oracle Database Administrator's Guide 11g)
References
NOTE:460506.1 - ORA-00845 When Starting Up An 11g Instance With AMM Configured.
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