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SUSE Linux Platform Notes

This topic includes the information on the following adjustments:

I/O Scheduler

The I/O scheduler for SUSE Linux is responsible for ordering the I/O requests submitted to a storage device. On SUSE Linux 15, it may default to BFQ (Budget Fair Queueing) which is known to cause performance issues with InterSystems IRIS. InterSystems recommends changing this setting to NONE. For details on changing the I/O scheduler, see the SUSE documentation: Tuning I/O PerformanceOpens in a new tab.


Setting the I/O scheduler to NONE may not be optimal for all use cases. Users should test the system’s application workload after making any changes.

Shared Memory Limits

The default shared memory limits (shhmax and shmall) on SUSE Linux 32-bit platforms are too small for InterSystems IRIS, and can be changed in the proc file system without a restart.

InterSystems IRIS uses shared memory for database buffers, global buffers, routine buffers, as well as license use. If the machine is being used only for InterSystems IRIS, InterSystems recommends setting the shared memory to approximately half the total memory. For more information, see Memory Planning in System Resource Planning and Managment, as well as Memory and Startup Settings and Determining License Capacity and Usage in the System Administration Guide.


The recommendations to change the shared memory limits do not apply to SUSE Linux 64-bit systems.

For example, to allow 512 MB, type the following commands:

#sets shmall and shmmax shared memory
echo 536870912 >/proc/sys/kernel/shmall     #Sets shmall to 512 MB
echo 536870912 >/proc/sys/kernel/shmmax     #Sets shmmax to 512 MB

You can put these commands into a script that is run at startup. The SUSE Linux product documentation recommends you put the commands in the /etc/init.d/boot.local script file.

You can change the settings for the system memory user limits by modifying a file called /etc/profile.local. Add lines similar to the following:

#sets user limits (ulimit) for system memory resources
ulimit -v 512000     #set virtual (swap) memory to 512 MB 
ulimit -m 512000     #set physical memory to 512 MB

In this same file, you can permanently change the values for the PATH and CLASSPATH parameters by adding lines similar to the following:

#sets env values PATH and CLASSPATH
export PATH=$PATH:/usr/iris/bin:/path/to/j2sdk/bin:/.


To avoid the risk of losing your changes during system upgrades, do not change the /etc/profile file.

Locked-in Memory

On Linux platforms, if shared memory is allocated in huge pages, they are automatically locked in memory and no further action is required. See Configuring Huge Pages on Linux for information about allocating huge pages.

If not using huge pages, you can configure InterSystems IRIS to lock the shared memory segment in memory to prevent paging. This is described in the LockSharedMemory section of the “memlock” entry in the Configuration Parameter File Reference.

Otherwise, you must increase the maximum size that may be locked into memory. See the Locked-in Memory section of the Red Hat Linux Platform Notes in this chapter for instructions.

Using Kerberos

To use Kerberos on the SUSE Linux platform, you must install the krb5-devel package in addition to the krb5-libs package. Installing krb5-devel establishes the required symbolic links for using Kerberos. The package is required for production environments, not only development environments. See the SUSE documentationOpens in a new tab web site for more information about these components.

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