Administering Oracle Database on Linux

rongshiyuan發表於2012-08-18
OracleDatabaseLinux
 
Oracle® Database Administrator’s Reference
10g Release 1 (10.1) for UNIX Systems: AIX-Based Systems, hp HP-UX PA-RISC (64-bit), hp Tru64 UNIX, Linux x86, and Solaris Operating System (SPARC)
Part No. B10812-01
 

C Administering Oracle Database on Linux

This appendix contains information about administering Oracle Database on Linux. It contains the following sections:

Linux x86 Only: Extended Buffer Cache Support

Oracle Database can allocate and use more than 4 GB of memory for the database buffer cache. This section describes the limitations and requirements of the extended buffer cache feature on Linux x86.


See Also:

For more information about the extended cache feature, see Oracle Database Concepts.


In-Memory File System

To use the extended buffer cache support, create an in-memory file system on the /dev/shm mount point equal in size or larger than the amount of memory that you intend to use for the database buffer cache:

  1. For example, to create an 8 GB file system on the /dev/shm mount point, enter the following command as the root user: 

    # mount -t shm shmfs -o size=8g /dev/shm

  2. Add an entry in the /etc/fstab file, similar to the following, to ensure that the in-memory file system is mounted when the system reboots: 

    none /dev/shmfs shmfs size=8g 0 0

When Oracle Database starts with the extended buffer cache feature enabled, it creates a file in the /dev/shm directory that corresponds to the Oracle buffer cache.


Note:

If an in-memory file system is already mounted on the /dev/shm mount point, ensure that its size is equal to or larger than the amount of memory that is used for the database buffer cache.


USE_INDIRECT_DATA_BUFFERS Parameter

To enable the extended buffer cache feature, set the USE_INDIRECT_DATA_BUFFERS parameter to TRUE in the parameter file. Doing this allows Oracle Database to specify a larger buffer cache.


Dynamic Cache Parameters

If the extended cache feature is enabled, you must use the DB_BLOCK_BUFFERS parameter to specify the database cache size.

Do not use the following dynamic cache parameters while the extended cache feature is enabled:

  • DB_CACHE_SIZE

  • DB_2K_CACHE_SIZE

  • DB_4K_CACHE_SIZE

  • DB_8K_CACHE_SIZE

  • DB_16K_CACHE_SIZE


Limitations

The following limitations apply to the extended buffer cache feature:

  • You cannot create or use tablespaces with non-default block size. You can create tablespaces using only the block size specified by the DB_BLOCK_SIZE parameter.

  • You cannot change the size of the buffer cache while the instance is running.


See Also:

For more information about the default block size used by the CREATE TABLESPACE command, see the Oracle Database SQL Reference.


Note:

The default VLM window size is 512 MB. This memory size is allocated to the process’s address space. To increase or decrease this value, set the VLM_WINDOW_SIZE environment variable to the new size in bytes. For example, to set the VLM_WINDOW_SIZE to 256 MB, enter the following: 
$ export VLM_WINDOW_SIZE=268435456

The value you specify for the VLM_WINDOW_SIZE environment variable must be a multiple of 64 KB.



Red Hat Enterprise Linux 3 Only: VLM Window Size

To accommodate the VLM window size, you need to increase the default maximum size of the per-process max locked memory. To increase it, add the following lines to the /etc/security/limits.conf file, where oracle is the user that administers the database: 

oracle          soft    memlock        3145728oracle          hard    memlock        3145728

If you use ssh to log in to the system, add the following line to the /etc/ssh/sshd_config file to enable the default values to be used when an ssh session is started: 

UsePrivilegeSeparation no
 

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