8.2.1 About Performance Problems

Many performance issues are the result of configuration errors. You can avoid such errors by using a validated configuration that has been pre-tested fore the supported software, hardware, storage, drivers, and networking components. A validated configuration incorporates the best practices for Oracle Linux deployment and has undergone real-world testing of the complete stack. Oracle publishes more than 100 validated configurations, which are freely available for download. You should also refer to the release notes for recommendations on setting kernel parameters.

A typical problem involves out of memory errors and generally poor performance when running Oracle Database. The cause of this problem is likely to be that the system is not configured to use the HugePages feature for the System Global Area (SGA). With HugePages, you can set the page size to between 2MB and 256MB, so reducing the total number of pages that the kernel needs to manage. The memory associated with HugePages cannot be swapped out, which forces the SGA to remain resident in memory.

The following utilities allow you to collect information about system resource usage and errors, and can help you to identify performance problems caused by overloaded disks, network, memory, or CPUs:

dmesg

Displays the contents of the kernel ring buffer, which can contain errors about system resource usage. Provided by the util-linux-ng package.

dstat

Displays statistics about system resource usage. Provided by the dstat package.

free

Displays the amount of free and used memory in the system. Provided by the procps package.

iostat

Reports I/O statistics. Provided by the sysstat package.

iotop

Monitors disk and swap I/O on a per-process basis. Provided by the iotop package.

ip

Reports network interface statistics and errors. Provided by the iproute package.

mpstat

Reports processor-related statistics. Provided by the sysstat package.

sar

Reports information about system activity. Provided by the sysstat package.

ss

Reports network interface statistics. Provided by the iproute package.

top

Provides a dynamic real-time view of the tasks that are running on a system. Provided by the procps package.

uptime

Displays the system load averages for the past 1, 5, and 15 minutes. Provided by the procps package.

vmstat

Reports virtual memory statistics. Provided by the procps package.

Many of these utilities provide overlapping functionality. For more information, see the individual manual page for the utility.

See Section 4.2.3, “Parameters that Control System Performance” for a list of kernel parameters that affect system performance.