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Maximize performace of Oracle and IBM DB2

Commercial databases such as Oracle and IBM DB2 can maximize performance by using raw I/O. One may use the raw command for both IDE and SCSI devices. This will map a raw device to a blocked device for an entire disk partition. To see if your system is using raw I/O issue the command: raw -a

* Configuration file: /etc/sysconfig/rawdevices

Add entries to this file to invoke raw I/O upon system boot.
* Devices: /dev/raw/raw??
* Raw device controller: /dev/rawctl
* Sample use of command: raw /dev/raw/raw1 /dev/hdb5
* One must be of group disk to use the raw device or change permissions:

chmod a+r /dev/rawctl

chmod a+r /dev/hdb5
chmod a+rw /dev/raw/raw1

Note: The above information applies to Red Hat distributions. This info may be different for other distributions. i.e. S.U.S.E. uses /dev/raw1 as a device and /dev/raw as the controller.
You can mimic Red Hat behavior with a symbolic link: ln -s /dev/your_raw_controller /dev/rawctl


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