Dear
Readers,
My
name is Franz Devantier, creator of this blog. I am an Oracle Certified
Professional (OCP DBA 11g) Security DBA.
I will be sharing with you the basic duties of an Oracle DBA, and also
some of the undocumented, and not so well known tasks.
I will make a deal with you: If you refer me to a company that needs
database support, from a few hours per week to full time, and I am able to sign
a contract with them.
Then I will give you 10% of the
monthly contract or deal price every month.
When the contract ends, and we re-sign the contract, I will again give
you 10% of the monthly contract price.
This will go on until the company no longer employs or contracts me or
my agents to look after their databases.
I can do this, because that 10% is my
marketing budget. When we re-sign the
contract, in the future, it may depend on you giving the thumbs up again, and
that is worth 10% of the monthly contract price, to be given to you as
commission.
Oracle
Database Preinstallation – Part 10
Configuring
Kernel Parameters for Linux
When you run Oracle Universal
Installer (OUI), any kernel parameters that are not set to the minimal
requirements, will be noted. Although it
is possible to run the “fixup script” to set the kernel parameters, and then
continue with the installation, it is better practice to verify your kernel
parameters, before you start the installation with OUI. The “fixup script”, will be setting the
kernel parameters to minimal values, where they were below the minimal
values. Oracle recommends that you
should tune and optimize these kernel parameters, to get the most out of your
oracle Installation.
Kernel parameters, minimal values
|
Parameter
|
Value
|
File
|
|
Semmsl
|
250
|
/proc/sys/kernel/sem
|
|
Semmns
|
32000
|
|
|
Semopm
|
100
|
|
|
Semmni
|
128
|
|
|
Shmall
|
2097152
|
/proc/sys/kernel/shmall
|
|
Shmmax
|
Minimum: 536870912
=> 32-bit Linux
Systems
Maximum: A value that is 1
byte less than 4 GB, or 4294967295
Recommended: More than half
the physical memory
=> 64-bit Linux
Systems
Maximum: A value that is 1
byte less than the physical memory
Recommended: More than half
the physical memory
|
/proc/sys/kernel/shmmax
|
|
Shmmni
|
4096
|
/proc/sys/kernel/shmmni
|
|
file-max
|
6815744
|
/proc/sys/fs/file-max
|
|
aio-max-nr
|
1048576
Note: This value limits
concurrent outstanding requests and should be set to avoid I/O subsystem
failures.
|
/proc/sys/fs/aio-max-nr
|
|
ip_local_port_range
|
Minimum: 9000
Maximum: 65500
Verifying UDP and TCP
Kernel Parameters
|
/proc/sys/net/ipv4/ip_local_port_range
|
|
rmem_default
|
262144
|
/proc/sys/net/core/rmem_default
|
|
rmem_max
|
4194304
|
/proc/sys/net/core/rmem_max
|
|
wmem_default
|
262144
|
/proc/sys/net/core/wmem_default
|
|
wmem_max
|
1048576
|
/proc/sys/net/core/wmem_max
|
When you verify the
parameters, keep in mind that the “fixup script”, does not change the value of
any of the kernel parameters that are greater than the minimal values.
Displaying and
Changing Kernel Parameter Values
The below command will
display the semaphore kernel parameter and its values.
$ /sbin/sysctl –a |grep sem
kernel.semmsl = 250
kernel.semmns = 32000
kernel.semopm = 100
kernel.semni = 128
The below command
will display the details of the shared memory segments.
$ /sbin/sysctl –a
|grep shm
kernel.shmmax =
68719476736
kernel.shmall =
4294967296
kernel.shmmni =
4096
The below command
will display the maximum number of file handles
$ /sbin/sysctl –a
|file-max
fs.file-max =
98480
The Below command
will display a range of port numbers
$ /sbin/sysctl -a | grep ip_local_port_range
net.ipv4.ip_local_port_range
= 32768 61000
$ /sbin/sysctl -a | grep
rmem_default
net.core.rmem_default
= 229376
$ /sbin/sysctl -a | grep
rmem_max
net.core.rmem_max
= 131071
$ /sbin/sysctl -a | grep
wmem_default
net.core.wmem_default
= 229376
$ /sbin/sysctl -a | grep
wmem_max
net.core.wmem_max
= 131071
$ /sbin/sysctl -a | grep
aio-max-nr
fs.aio-max-nr =
1048576
Now that you have
gathered the information, you can compare it against the table of default
values. If any of the kernel parameters
is different from the minimal value, then you can do the following.
Edit the
/etc/sysctl.conf file, and you can either add lines that are missing or edit
the values of the entries that are there.
For the semaphore parameters, you must specify all four values. If any of the current values are larger than
the minimum value, then you can leave it at the minimum.
Added these entries, in this
case:
fs.aio-max-nr = 1048576
fs.file-max = 6815744
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
net.ipv4.ip_local_port_range =
9000 65500
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576
Because we have added the
values to the /etc/sysctl.conf file, they will persist when we restart the
operating system. To change the current
value of the kernel parameters:
$ /sbin/sysctl –p
Review the output to make sure
that all the values are correct. If not,
then edit /etc/sysctl.conf again, then enter the /sbin/sysctl –p again, until
you are happy with the output.
Then to further confirm, you
can enter:
$ /sbin/sysctl -a |less
When
you are satisfied with the results, and remember we have focussed on Oracle
Linux on intel hardware here, then you can either restart the computer, or run
the command sysctl –p to make the changes in the /etc/sysctl.conf file
available in the active kernel memory.
Franz
Devantier,
Need
a database health check?
devantierf@gmail.com
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