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Oracle OS Kernel Parameters
Oracle Tips by Burleson Consulting |
OS kernel parameters
Oracle’s OS specific installation instructions provide guidelines
for the OS configuration, but the settings for the OS parameters can
make an enormous difference in Oracle performance.
Because Oracle runs on over 60 different operating systems from a
mainframe to a Macintosh, it is impossible to cover every single
platform. However, the common configuration issues for UNIX and
Microsoft Windows platforms will be presented.
Server Settings for Windows Servers
Windows servers for Oracle are relatively simple when compared to
UNIX-based servers. There are only a few major points to cover to
ensure that the Windows server is optimized for an Oracle database.
The larger Windows servers (e.g. the UNISYS ES7000 servers) can have
up to 32 CPUs and hundreds of gigabytes of RAM. They can support
dozens of Oracle instances, but many third party applications can
hog server resources, causing Oracle performance issues.
Kernel setting for UNIX and Linux servers
In UNIX and Linux, there is much more flexibility in configuration
and hundreds of kernel setting that can benefit database
performance. Table 14.1 lists some of the most common kernel
parameters that influence Oracle:
|
Parameter Name |
Description |
Default Value |
Set By the DBA |
|
shmmax |
The maximum size, in bytes, of a single shared memory
segment. For best performance, it should be large enough to
hold the entire SGA. |
1048576 |
YES |
|
shmmin |
The minimum size, in bytes, of a single shared memory
segment. |
1 |
YES |
|
shmseg |
The maximum number of shared memory segments that can be
attached (i.e. used) by a single process. |
6 |
YES |
|
shmmni |
This determines how many shared memory segments can be on
the system. |
100 |
YES |
|
shmmns |
The amount of shared memory that can be allocated
system-wide. |
N/A |
NO |
Table 14.1:
OS Parameters
For details, the OS specific Oracle installation guide should be
consulted for details. One of the most common problems with Oracle
server configuration is sub-optimal I/O. For example, the most
important thing with Linux is enabling direct I/O on the underlying
file system. Without that being enabled, Linux will cache files both
in the system buffer cache and in SGA. That double caching is
unnecessary and will deprive the server of RAM resources. The
following section provides a closer look by outlining some of the
important Oracle parameters for performance.
SEE CODE DEPOT FOR FULL SCRIPTS
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This is an excerpt from my latest book "Oracle
Tuning: The Definitive Reference".
You can buy it direct from the publisher for 30%-off and get
instant access to the code depot of Oracle tuning scripts: |
http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm
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