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System Setting Required to Run Oracle Software

Oracle Database Tips by Donald Burleson

Located in the Code Depot for this book (see Appendix B) is a script called  This script should be run as the root user on each node. It will automatically write each of the settings described in the following section to the necessary system configuration files.




kernel.shmni (leave at default)

The maximum number of system-wide shared memory segments.

kernel.shmmax =2147483648

The maximum size of each shared memory segment. It should be set to a minimum of half the real memory. Setting it at 2 gigabytes will not cause trouble even if there is minimal RAM installed. It is saved in file /etc/sysctl.conf.

kernel.shmall (leave at default)

Defines the maximum amount of shared memory that may be in use at any time on the system.

kernel.shmseg (leave at default)

Defines the maximum number of shared memory segments to which a single process can attach.


Maximum number of semaphores per set.


Total number of semaphores in the system.


Maximum number of operations per semop call.


Maximum number of semaphore sets.

The previous four semaphore parameters are saved in /etc/sysctl.conf  using the following syntax, delimited by white space:

### kernel.sem=semmsl semmns semopm semmni

kernel.sem=250 32000 100 128

fs.file-max = 65536

Determines the maximum number of files that any single process can open. It is saved in file /etc/sysctl.conf.



Each network socket is allocated a send buffer for outbound packets and a receive socket for inbound packets. To support high data rates required for Oracle's cache fusion, these four parameters are increased. It is saved in file /etc/sysctl.conf.




ulimit ?u 16384

Sets the maximum number of processes that a user can start. The Oracle user starts the database, which requires a high limit. It is saved in file /etc/rc.local.

Table 4.2: System settings and descriptions

A few system settings are specific to a RAC on a Firewire configuration. The following table lists those settings. These settings are also included in the script.

System Setting


options sbp2 sbp2_exclusive_login=0

post-install sbp2 insmod sd_mod

post-remove sbp2 rmmod sd_mod

Settings specific to the kernel modified for dual logging on the firewire drive. It is saved in the file  /etc/modules.conf.

Table 4.3: RAC specific settings on Firewire confiruration

Running the Script

Run the os_prep.shscript as shown in Figure 4.5. When the script has finished, use the init 6 command to reboot the node. Afterward, proceed to the next node and follow the same steps to install the modified kernel.  Run the script and reboot.

Verifying the External Drive

With the modified kernel installed, the os_prep.shrun, and each node rebooted, the external drive should now be available to each node. The commands shown in Figure 4.6 are used to verify that a given node has detected the external drive. If the external drive has been partitioned, the fdisk ?l | grep sd command will return one line for the disk and one line for each partition. If the external drive is not detected, which is common for a first boot to the new kernel, another reboot of the node in question will usually fix the problem.

Learn More about PC RAC:

If you want to learn RAC at home, get the bestselling book "Personal Oracle Real Application Clusters" by Edward Stoever.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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