Category Archives: Maximum Availability Architecture

Another problem with “KSV master wait” and “ASM file metadata operation”

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My customer today tried to do a duplicate on a cluster. When preparing the auxiliary instance, she noticed that the startup nomount was hanging forever: Nothing in the alert, nothing in the trace files.

Because the database and the spfile were stored inside ASM, I’ve been quite suspicious…

The ASM trace files had the following entries:

The ASM instance had the following sessions waiting:

OMS?

Around 12:38:56, another colleague in the office added a disk to one of the disk groups, through Enterprise Manager 12c!

But there were no rebalance operations:

It’s not the first time that I hit this type of problems. Sadly, sometimes it requires a full restart of the cluster or of ASM (because of different bugs).

This time, however, I have tried to kill only the foreground sessions waiting on “ASM file metadata operation”, starting with the one coming from the OMS.

Surprisingly, after killing that session, everything was fine again:

I never add disks via OMS (I’m a sqlplus guy ;-)) , I wonder what went wrong with it 🙂

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Ludovico

DBMS_QOPATCH, datapatch, rollback, apply force

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I am working for a customer on a quite big implementation of Cold Failover Cluster with Oracle Grid Infrastructure on Linux. I hope to have some material to publish soon about it! However, in this post I will be talking about patching the database in a cold-failover environment.

DISCLAIMER: I use massively scripts provided in this great blog post by Simon Pane:

https://www.pythian.com/blog/oracle-database-12c-patching-dbms_qopatch-opatch_xml_inv-and-datapatch/

Thank you Simon for sharing this 🙂

Intro

We are not yet in the process of doing out-of-place patching; at the moment the customer prefers to do in-place patching:

  • evacuate a node by relocating all the databases on other nodes
  • patching the node binaries
  • move back the databases and patch them with datapatch
  • do the same for the remaining nodes

I beg to disagree with this method, being a fan of having many patched golden copies distributed on all servers and patching the databases by just changing the ORACLE_HOME and running datapatch (like Rapid Home Provisioning does). But, this is the situation today, and we have to live with it.

Initial situation

  • Server 1, 2 and 3: one-off 20139391 applied
  • New database created

cfc_qopatch1When the DBCA creates a new database, in 12.1.0.2, it does not run datapatch by default, thus, the database does not have any patches installed.

However, this specific one-off patch does not modify anything in the database (sql_patch=false)

and the datapatch runs without touching the db:

Next step: I evacuate the server 2 and patch it, then I relocate my database on it

cfc_qopatch2

Now the database is not at the same level of the binaries and need to be patched:

The column CONSTITUENT is important here because it tells us what the parent patch_id is. This is the column that we have to check when we want to know if the patch has been applied on the database.

Now the patch is visible inside the dba_registry_sqlpatch:

Notice that the child patches are not listed in thie view.

Rolling back

Now, one node is patched, but the others are not. What happen if I relocate the patched database to a non-patched node?

cfc_qopatch3

The patch is applied inside the database but not in the binaries!

If I run datapatch again, the patch is rolled back:

The patch has been rolled back according to the datapatch, and the action is shown in the dba_registry_sqlpatch:

But if I look at the logfile, the patch had some errors:

Indeed, the patch looks still there:

If I try to run it again, it does nothing/it fails saying the patch is not there:

What does it say on the patched node?

Whaaat? datapatch there says that the patch IS in the registry and there’s nothing to do. Let’s try to force its apply again:

Conclusion

I’m not sure whether it is safe to run the patched database in a non-patched Oracle Home. I guess it is time for a new SR 🙂

Meanwhile, we will try hard not to relocate the databases once they have been patched.

Cheers

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Ludo

Recording of “Rapid Home Provisioning” webinar for the RAC SIG

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Yesterday I have presented the Oracle Rapid Home Provisioning technology for the RAC SIG, you can find the recording on YouTube:

Cheers

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Ludo

Rapid Home Provisioning

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In a few days I will give a presentation at UKOUG Tech15 about Rapid Home Provisioning, it will be the first time that I present this session in public.

I usually like to give the link to the material to my audience, so here we go:

Slides:

Demo:

Enjoy
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Ludovico

Oracle Active Data Guard and Global Data Services in Action!

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In a few days I will give a presentation at UKOUG Tech15 about Global Data Services, it will be the first time that I present this session.

I usually like to give the link to the material to my audience, so here we go:

Credits

I have to give special credits to my colleague Robert Bialek. I’ve got a late confirmation for this session and my slide deck was not ready at all, so I have used a big part of his original work. Most of the content included in the slides has been created by Robert, not me. (Thank you for your help! :-))

Slides

Demo recording

Demo script

And the script to revert the demo:

Cheers

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Ludovico

 

Oracle Database on ACFS: a perfect marriage?

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Update: I will give this presentation at UKOUG Tech15, Wed 9 December at 14:30.

This presentation has had a very poor score in selections for conferences (no OOW, no DOAG) but people liked it very much at Paris Oracle Meetup.  The Database on ACFS is mainstream now, thanks to the new ODA releases. Having some knowledge about why and how you should run (not) Databases on ACFS is definitely worth a read.

Slides

Demo 1 recording

Demo 2 recording

Demo script (DB ACFS clone from Standby Database)

 

Comments are, as always, very appreciated 🙂

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Ludo

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

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Ludovico

Grid Infrastructure 12c: Recovering the GRID Disk Group and recreating the GIMR

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Losing the Disk Group that contains OCR and voting files has always been a challenge. It requires you to take regular backups of OCR, spfile and diskgroup metadata.

Since Oracle 12cR1, there are a few additional components you must take care of:

– The ASM password file (if you have Flex ASM it can be quite critical)

– The Grid Infrastructure Management Repository

Why ASM password file is important? Well, you can read this good blog post form my colleague Robert Bialek: http://blog.trivadis.com/b/robertbialek/archive/2014/10/26/are-you-using-oracle-12c-flex-asm-if-yes-do-you-have-asm-password-file-backup.aspx

So the problem here, is not whether you should back them up or not, but how you can restore them quickly.

Assumptions: you back up regularly:

ASM parameter  file:

Oracle Cluster Registry:

ASM Diskgroup Metadata:

ASM password file:

What about the GIMR?

According to the MOS Note: FAQ: 12c Grid Infrastructure Management Repository (GIMR) (Doc ID 1568402.1), there is no such need for the moment.

Weird, huh? The -MGMTDB itself contains for the moment just the Cluster Health Monitor repository, but expect to see its important increasing with the next versions of Oracle Grid Infrastructure.

If you REALLY want to back it up (even if not fundamental, it is not a bad idea, after all), you can do it.

The -MGMTDB is in noarchivelog by default. You need to either put it in archivelog mode (and set a recovery area, etc etc) or back it up while it is mounted.

Because the Cluster Health Monitor (ora.crf)  depends on it, you have to stop it beforehand:

Then you can operate with -MGMTDB:

Now, imagine that you loose the GRID diskgroup (nowadays, with the ASM Filter Driver, it’s more complex to corrupt a device by mistake, but let’s assume that you do it):

The cluster will not start anymore, you need to disable the crs, reboot and start it in exclusive mode:

 

Then you can recreate the GRID disk group and restore everything inside it:

Finally, the last missing component: the GIMR.

You can recreate it or restore it (if you backed it up at some point in time).

Let’s see how to recreate it:

Conclusion

Recovering from a lost Disk Group / Cluster is not rocket science. Just practice it every now and then. If you do not have a test RAC, you can build your lab on your laptop using the RAC Attack instructions. If you want to test all the scenarios, the RAC SIG webcast: Oracle 11g Clusterware failure scenarios with practical demonstrations by Kamran Agayev is the best starting point, IMHO. Just keep in mind that Flex ASM and the GIMR add more complexity.

HTH

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Ludovico

Another successful RAC Attack in Geneva!

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ninja-suisseLast week I have hosted the second Swiss RAC Attack workshop at Trivadis offices in Geneva. It has been a great success, with 21 total participants: 5 Ninjas, 4 alumni and 14 people actively installing or playing with RAC 12c on their laptops.

Last year I was suprised by a participant coming fron Nanterre. This year two people came directly from Moscow, just for the workshop!

We’ve got good pizza and special beer: Chimay , Vedett, Duvel, Andechs…

Last but not least, our friend Marc Fielding was visiting Switzerland last week, so he took the opportunity to join us and make the workshop even more interesting! 😀
 DSC07173 DSC07164 DSC07183 DSC07148 DSC07147 DSC07144 DSC07142 DSC07154 DSC07153 DSC07152 DSC07151

Looking forward to organize it again in one year! Thank you guys 🙂

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Ludovico

RAC Attack! 12c is back to Geneva!

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ninja-suisseVersion française ici.

After a great success in 2014, RAC Attack! comes back to Geneva!
Set up an Oracle Real Application Clusters 12c environment on your laptop, try advanced configurations or simply take the opportunity to discuss about Oracle technology with the best experts in Suisse Romande!
Experienced volunteers (ninjas) will help you  address any related issues and guide you through the setup process.

Where? Trivadis office, Chemin Château-Bloch 11, CH1219 Geneva

When? Thursday September 17th, 2015, from 17h00 onwards

Cost? It is a FREE event! It is a community based, informal and enjoyable workshop. You just need to bring your own laptop and your desire to have fun!

Confirmed Ninjas:
Ludovico Caldara – Oracle ACE, RAC SIG Chair & co-auteur RAC Attack
Eric Grancher – Membre OAK Table & Senior DBA
Jacques Kostic – OCM 11g & Senior Consultant chez Trivadis

Limited places! Reserve your seat and T-shirt now!

tshirt_racattack_2015Agenda:
17.00 – Welcome and T-shirt distribution
17.30 – RAC Attack 12c part I
19.30 – Pizza and Beers! (sponsored by Trivadis)
20.00 – RAC Attack 12c part II
22.00 – Group photo and wrap-up!!

Still undecided? Look at what we did last year!

This event is sold out. No more seats available, sorry! Would you be interested in joining the event next year? Drop me an email!