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.
Contact: Franz
Oracle
Database Preinstallation – Part 1
These are
the tasks that you must complete, before you run Oracle Universal Installer
(OUI).
Generally
speaking there are two things that you should do before installing the Oracle
software. Firstly you should download
the installation manual for your specific manual, and perform the
pre-installation tasks. Secondly if you
are going to use Oracle Automatic Storage Management (ASM), or Oracle restart,
then you should start off by installing Oracle Grid Infrastructure.
My
notes are relevant to Linux and Unix, because with windows, most of these
pre-installation tasks are transparent, and you can usually just get away with,
putting the installation disk in and running it. Actually I will be focussing on Linux,
because Oracle has invested a lot into Linux, and secondly it is very
convenient to load the Linux operating system onto your laptop or workstation,
or virtual OS. Oracle Linux has a free
version, which you can download and install.
So we are looking at Oracle linux really, which is essentially Red Hat.
Logging in to the System as root
Firstly
you need to complete several tasks as the root user. If the organization has a problem with giving
the DBA the root password, then you will need to work very closely with the Sys
Admin. In windows you really just need
an administrator login, and you are good to go.
You
must install the software using a X Windows utility, or a X terminal, or any
other system that can use or invoke X Server software. If you are using silent mode installation,
the you don’t need X Windows.
Installing from X Windows workstation or X
Terminal:
=>
Firstly you need to start your local terminal session, which could be something
like “xterm”.
=>
If you are not going to install the software on the local system, then you need
to enable the remote host to display X applications on your local X Server or
workstation.
You
can achieve this something like:
$
xhost <fully qualified host name>
=>
If you are going to install the software on the remote system, then use ssh,
rlogin or telnet to connect to the system on which you want to install the
software. If you can use telnet on your
site, then you have inherent issues, and I would suggest that you get an Oracle
security expert to advice you.
=>
If you are not logged in as root, then you must first do something like:
$sudo
su root
Otherwise
you must work closely with the companies sys admin.
=>
To install the Oracle software on Linux, you may have to read through the
specific X server documentation or request support from the specific
vendors. However the process should run
something like this:
1.)
Start your X server software
2.)
Configure your X server to allow remote hosts to display X application on your
workstation or local system.
3.)
Connect to the remote server or where you want to install the Oracle software,
and start your terminal or X windows session on that server. For example an xterm session. You may need to first logon to root, or do a
“sudo” or “sudo su” to root, before you can proceed.
Now
that you are logged onto the server where you will install the software, and
have some sort of X Windows facilities, you are ready to verify the Hardware
Requirements for the installation.
Verifying the Hardware Requirements for
11.2
We
will check that we meet the minimal requirements. If there has been time for planning, then you
may have a set of hardware requirements that exceed the minimal
requirements. The areas that we will
check include the Memory requirements, System architecture, Disk space
requirements, and Display requirements.
Memory Requirements:
Minimum
1GB of RAM, recommended at least 2GB of RAM.
One
way to determine the size of the RAM on a linux box is:
$
grep MemTotal /proc/meminfo
If
the size of the RAM is less than the minimal required size, then you must first
install more RAM before continuing. The
installation will abend if you try to install without enough RAM.
You
also need to take into account the relationship between installed RAM, and the
configured swap space. There are
specific recommendations by Oracle, and it is good to try to stay within those
parameters.
RAM
|
Swap Space
|
Between
1GB and 2GB
|
1.5
times the size of the RAM, 1.5GB to 3GB
|
Between
2GB and 16GB
|
Swap
space should be equal to the size of the RAM
|
More
than 16GB
|
Swap
space should not be larger than 16GB
|
If
Oracle does start using too much swap space, during operations, you could have
a drastically reduced performance throughput.
On Linux you can enable the HugePages feature. HugePages are basically used for
memory-mapped files. If you are using HugePages,
then you should deduct the memory allocated to HugePages from your RAM, before
calculating the relationship between RAM and swap space. You also need to verify that after deducting
your HugePages from RAM, you still have at least 1GB of RAM left.
On
linux you can use a command like this to verify the available RAM and swap
space.
$
free
Remember
that as the interactions with the server change, from busy to quite, your
available RAM and swap space readings are going to keep changing; so you will
need to perform this step under various stress conditions, to arrive at
meaningful values. It may also be useful
to get recommendations from you OS vendor for specific guidelines on the RAM
Swap space settings.
Using Automatic Memory Management (AMM)
From
11g onwards, AMM requires more shared memory than before, which on linux is
defined in “/dev/shm”, as well as using more file descriptors. Two parameters in the database must be
smaller than the size of the defined shared memory. MEMORY_MAX_TARGET or MEMORY_TARGET, typically
MEMORY_MAX_TARGET would have the larger value, or would be equal to
MEMORY_TARGET. You would need to add values
from all the Oracle instances on the computer, to properly determine the size
to assign to the shared memory.
On
Linux especially if the operating system mount size that has been defined is
too small for the instance being started, defined in “/dev/shm”, then you will
get the ORA-00845 error, when you try to start the instance. The above mentioned Oracle memory variables,
define the total size of the combined System Global Area (SGA), and Program
Global Area (PGA).
The
other variable that can bite is the file descriptors. There should be at least 512 times the Oracle
variable PROCESSES defined. If the file
descriptors is not sized correctly then you will get an Oracle error:
ORA-27123. Potentially you may also get
the Linux error “EMFILE (Too many open files)”, especially with regards to
non-Oracle related processes.
It
is quite easy to determine the amount of shared memory available.
$
df –h /dev/shm/
Keep
in mind that if you use the parameter LOCK_SGA, then you can’t use
MEMORY_MAX_TARGET or MEMORY_TARGET. Also
if you have defined HugePages on the Linux level, then you can’t use
MEMORY_MAX_TARGET or MEMORY_TARGET.
For
example, if the shared memory file system allocation on your server is 1GB, and
you have set MEMORY_MAX_TARGET = to 2GB, then you will get the following
errors, when you try to start the database up.
ORA-00845
MEMORY_MAX_TARGET not supported on
this system
ORA-01078 Failure in processing system parameters
To
address the ORA-00845 error, you can increase the “/dev/shm” mountpoint size.
For
example:
$
mount –t tmpfs shmfs -0 size=7g /dev/shm
Then
you will need to make this change persistent across system restarts, by adding
an entry in the “/etc/fstab”
For
example:
$
smfs /dev/shm tmpfs size=7g 0
The
database name is typically limited to 8 characters, however sometimes a user
will have a requirement for the database to be named to something that is
longer than 8 characters. What happens
in this situation is:
Let’s
say the Global Database Name is longer than 8 characters.
DB_NAME
parameter is truncated to 8 characters.
DB_UNIQUE_NAME
parameter is set to the global name.
The
end result is that this is fairly transparent to the end user, but remember the
internal representation, for just in case you start to experience issues.
Franz Devantier,
Need a database health check?
devantierf@gmail.com
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