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Tuning Asynchronous I/O for Oracle 9i and 10g

filesystemio_options=asynch

This parameter is platform specific. By default, this parameter is set to none for Linux and thus needs

to be changed:

SQL> show parameter filesystemio_options;

NAME TYPE VALUE

------------------------------------ ----------- -----------

filesystemio_options string none

SQL>

The filesystemio_options can have the following values with Oracle9iR2:

• asynch: This value enables asynchronous I/O on file system files.

• directio: This value enables direct I/O on file system files.

• setall: This value enables both asynchronous and direct I/O on file system files.

• none: This value disables both asynchronous and direct I/O on file system files.

If you also want to enable Direct I/O Support which is available in Red Hat Enterprise Linux 4 or 5, set

filesystemio_options to "setall".

In Red Hat Enterprise Linux 3

It is recommended you use direct I/O ONLY for ext2, ext3, GFS, NFS and OCFS file

systems.

In Red Hat Enterprise Linux 4 and 5

It is strongly recommended to use the “setall” parameter for ext2, ext3, GFS, NFS and

OCFS file systems.

12.4. Tuning Asynchronous I/O for Oracle 9i and 10g

For Red Hat Enterprise Linux 3 it is recommended to set aio-max-size to 1048576 since Oracle

uses I/Os of up to 1MB. It controls the maximum I/O size for asynchronous I/Os.

Note

The aio-max-size tuning parameter is not applicable to the 2.6 kernel on Red Hat

Enterprise Linux 4 or 5.

To determine the maximum I/O size in bytes, execute:

$ cat /proc/sys/fs/aio-max-size

131072

To change the maximum number of bytes without reboot:

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 159 160

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Red Hat ENTERPRISE LINUX AS 2.1 - Guida di Installazione Pagina 39