The company just launched a set of Oracle 11gR2 RAC. When MEMORY_TARGET memory is set to 12 GB, an error is reported during startup:
ORA-00845: MEMORY_TARGET not supported on this system
00845,000 00, "MEMORY_TARGET not supported on this system"
// * Cause: The MEMORY_TARGET parameter was not supported on this operating system or/dev/shm was not sized correctly on Linux.
// * Action: Refer to documentation for a list of supported operating systems. Or, size/dev/shm to be at least the SGA_MAX_SIZE on each Oracle instance running on the system.
In Oracle 11g, SGA and PGA are automatically managed using the MEMORY_TARGET parameter. However, in Oracle 11gR2, if the MEMORY_TARGET parameter value is set too large, this error may occur.
Solution: Add/dev/shm and/dev/shm for shared memory.
/Dev/shm is a temporary file system (tmpfs ). Mount from/etc/fstab supports the standard parameter "size", which can be used to increase or decrease the tmpfs size on/dev/shm. if no size is set, its size is greater than MEMORY_TARGET.
To take effect immediately, use the following method:
# Umount tmpfs
# Mount-t tmpfs shmfs-o size = 14G/dev/shm
Enable Automatic mount for each restart of the OS. Modify the/etc/fstab file to change tmpfs to the following values:
Tmpfs/dev/shm tmpfs ults, size = 14G 0 0
If you directly modify/etc/fstab, restart the OS to make the parameter take effect.
Note: The size must be an integer.
Df-h: Check the modified/dev/shm size.
File System capacity used available % mount point
/Dev/mapper/vg00-lv_root
20 GB 11G 7.7G 59%/
/Dev/mapper/vg00-lv_home
97G 6.8G 86G 8%/home
/Dev/sda1 97 M 13 M 80 M 14%/boot
Tmpfs 14G 0 14G 0%/dev/shm
Instructions on the Oracle Official Website:
| ORA-00845 When Starting Up An 11g Instance With AMM Configured. [ID 460506.1] |
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Modified18-FEB-2010TypePROBLEMStatusPUBLISHED |
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In this Document
Symptoms
Changes
Cause
Solution
References
Applies to: Oracle Server-Enterprise Edition-Version: 11.1.0.6 to 11.2.0.2.0-Release: 11.1 to 11.2
Linux x86
Linux x86-64
Symptoms
On a Linux system, trying to start up an 11g instance cocould fail with the following error:
ORA-845: MEMORY_TARGET not supported on this system
In the alert log, you cocould or cocould not see the below messages:
ORA-04031 (errors)
OR
Starting ORACLE instance (normal)
WARNING: You are trying to use the MEMORY_TARGET feature.
This feature requires the/dev/shm file system to be mounted for
Least <size> bytes. The/dev/shm is either not mounted or is mounted
With available space less than this size.
Please fix this so that MEMORY_TARGET can work as expected.
Current available is <size> and used is <size> bytes. memory_target needs larger/dev/shm
If ORA-04031 is seen in the alert log, sometimes you can not establish new connections due to this problem.
ChangesInstalled 11g, or created a new database on 11g and is starting to use the AMM (Automatic Memory Management) feature.
CauseThis feature requires the/dev/shm file system to be mounted for at least % llu bytes.
/Dev/shm is either not mounted or is mounted with available space less than this size.
Explanation:
AMM (Automatic Memory Management) is a new feature in 11 which manages both SGA and PGA.
MEMORY_TARGET is used instead of SGA_TARGET and MEMORY_MAX_TARGET is used instead of SGA_MAX_SIZE (ults to MEMORY_TARGET ).
It uses/dev/shm on Linux. If max_target set over/dev/shm size, you get the error messages.
Solution1. If you are installing Oracle 11g on a Linux system, note that Memory Size (SGA and PGA), which sets
The initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, cannot be greater than the shared memory filesystem (/dev/shm) on your operating system. to resolve the current error, increase the/dev/shm file size. for example:
# Mount-t tmpfs shmfs-o size = 7g/dev/shm
Also, to make this change persistent internal SS system restarts, add an entry in/etc/fstab similar to the following:
Shmfs/dev/shm tmpfs size = 7g 0
2. This error may also occur if/dev/shm is not properly mounted. Make sure your df output is similar to the following:
$ Df-k
Filesystem 1K-blocks Used Available Use % Mounted on
...
Shmfs 6291456 832356 5459100 14%/dev/shm
3. if processing AMM is not possible due to lack of space on/dev/shm mount point, you can configure ASMM instead of AMM, I. e. set SGA_TARGET, SGA_MAX_SIZE and PGA_AGGREGATE_TARGET instead of MEMORY_TARGET.
| HugePages and Oracle Database 11g Automatic Memory Management (AMM) on Linux [ID 749851.1] |
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Modified05-NOV-2010TypeBULLETINStatusPUBLISHED |
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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
PurposeThis document discusses the interoperability of the Automatic Memory Management (AMM) feature introduced by Oracle DB 11g and the HugePages (HugeTLB) feature of the Linux OS kernel.
Scope and ApplicationThis 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 LinuxThe 11g AMM feature is enabled by the MEMORY_TARGET/MEMORY_MAX_TARGET instance initialization parameters (see Note 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 disabled (set to 0) for the database instance. (See also
Oracle
Database Administrator's Guide 11g)
ReferencesNOTE: 460506.1-ORA-00845 When Starting Up An 11g Instance With AMM Configured.
Related
Products
- Oracle Database Products> Oracle Database> Oracle Server-Enterprise Edition
- Unbreakable Linux and Virtualization> Unbreakable Linux> Operating System> Linux OS
Keywords
| HUGETLB; HUGEPAGES; database configuration assistant; DBCA |
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