Tag Archives: Linux

Migrating Oracle RAC from SuSE to OEL (or RHEL) live

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I have a customer that needs to migrate its Oracle RAC cluster from SuSE to OEL.

I know, I know, there is a paper from Dell and Oracle named:

How Dell Migrated from SUSE Linux to Oracle Linux

That explains how Dell migrated its many RAC clusters from SuSE to OEL. The problem is that they used a different strategy:

– backup the configuration of the nodes
– then for each node, one at time
– stop the node
– reinstall the OS
– restore the configuration and the Oracle binaries
– relink
– restart

What I want to achieve instead is:
– add one OEL node to the SuSE cluster as new node
– remove one SuSE node from the now-mixed cluster
– install/restore/relink the RDBMS software (RAC) on the new node
– move the RAC instances to the new node (taking care to NOT run more than the number of licensed nodes/CPUs at any time)
– repeat (for the remaining nodes)

because the customer will also migrate to new hardware.

In order to test this migration path, I’ve set up a SINGLE NODE cluster (if it works for one node, it will for two or more).

I have to setup the new node addition carefully, mainly as I would do with a traditional node addition:

  • Add new ip addresses (public, private, vip) to the DNS/hosts
  • Install the new OEL server
  • Keep the same user and groups (uid, gid, etc)
  • Verify the network connectivity and setup SSH equivalence
  • Check that the multicast connection is ok
  • Add the storage, configure persistent naming (udev) and verify that the disks (major, minor, names) are the very same
  • The network cards also must be the very same

Once the new host ready, the cluvfy stage -pre nodeadd will likely fail due to

  • Kernel release mismatch
  • Package mismatch

Here’s an example of output:

So the problem is not if the check succeed or not (it will not), but what fails.

Solving all the problems not related to the difference SuSE-OEL is crucial, because the addNode.sh will fail with the same errors.  I need to run it using -ignorePrereqs and -ignoreSysPrereqs switches. Let’s see how it works:

Then, as stated by the addNode.sh, I run the root.sh and I expect it to work:

Bingo! Let’s check if everything is up and running:

So yes, it works, but remember that it’s not a supported long-term configuration.

In my case I expect to migrate the whole cluster from SLES to OEL in one day.

NOTE: using OEL6 as new target is easy because the interface names do not change. The new OEL7 interface naming changes, if you need to migrate without cluster downtime you need to setup the new OEL7 nodes following this post: http://ask.xmodulo.com/change-network-interface-name-centos7.html

Otherwise, you need to configure a new interface name for the cluster with oifcfg.

HTH

—

Ludovico

Check the actual ulimits for all the running Oracle instances

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I’ve read the recent good post from my friend Rene on Pythian’s Blog about how to troubleshoot when user ulimits are different from what specified in limits.conf:

Quick Tip : Oracle User Ulimit Doesn’t Reflect Value on /etc/security/limits.conf

I would like to add my 2 cents:

Once you fix the problem, you may want to check (any maybe monitor) when an instance is running with a wrong value (and maybe encounter the famous Error message: Linux-x86_64 Error: 23: Too many open files in system).

This single line gives you an overview of all your instances at once:

If you find any wrong values, plan a restart before you encounter any error during peak hours!

—

Ludo

 

 

Smart Bash Prompt for Oracle

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If you are an Oracle customer who has several database versions running, you have to deal with scripts that become more and more complex to maintain. Depending on the version or the edition of your database, you may want to run different pieces of code. This forces you to get programmatically more information about your database version and edition (e.g., in order to run a statspack or AWR report if your software is either Enterprise or Standard).
The most common way to get information about the software is connecting to the database and getting it through a couple of selects. But what if you don’t have any running databases?
The ORACLE_HOME inventory has such information, and you can get it with a short shell function:

The snippet searches for a patchset entry in comps.xml to get the patch version rather than the base version (for releases prior to 11gR2 where out-of-place patching occurs). If a patchset cannot be found, it looks for the base version. Depending on the major release, the information about the edition is either in globalvariables.xml (11g, 12c) or in context.xml (10g).
When you call this “ohversion” function, you get both the Oracle version and the edition of your current ORACLE_HOME.
If you’re using the bash as user shell, you may want to take one step forward and  include this information in a much fancier bash prompt than the prompt by default:

2015_06_05_16_22_56_sso0419iAlthough this prompt may seem long, it has several advantages that save you a lot of typing:
• The newline character inside the prompt let’s you start typing commands on an almost empty line so you don’t have to worry about how long your command is.
• The full username@host:path can be copied and pasted quickly for scp commands.
• The time inside the square brackets is helpful to track timings.
• The indication of the current environment (version, edition, SID) lets you know which environment you’re working on.
• The leading number is the exit code of the last command ($?). It’s green when the exit code is zero and red for all other exit codes.
• Hash characters before and after the prompt mitigate the risk of copying and pasting the wrong line by mistake inside your session.

Note: this post originally appeared on IOUG Tips & Best Practices Booklet 9th edition.

Tips: Bash Prompt and Oracle

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You may want to check the NEW VERSION of this prompt here.

I disagree with default bash prompt. Do you? It’s quote common to work with long paths:

and, when working on multi-database environments I need to check my environment:

I currently use this prompt, instead:

What is ohvers?? I defined this function to get the version of oracle from my ORACLE_HOME variable:

Pros:

  • I have a blank line that separate my prompt from previous output
  • I get the system clock (useful when saving my konsole history. Did I say konsole?)
  • I can see my Oracle Environment before launching dangerous commands
  • I have an empty line to start my endless commands
  • I have a lot of sharps “#” : they are fine against wrong copy&paste operations…

Suggestions?