Category Archives: Oracle

When it comes to using Oracle, trust Oracle…

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A month ago, I saw this article published on the AWS architecture blog:

Disaster Recovery for Oracle Database on Amazon EC2 with Fast-Start Failover

I love seeing people suggesting Oracle Data Guard Fast-Start Failover for high availability. Nevertheless, there are a few problems with the architecture and steps proposed in the article.

I sent my comments via Disqus on the AWS blogging platform, but after a month, my comment was rejected, and the blog content hasn’t changed.

For this reason, I don’t have other places to post my comment but here…

  1. The link to the setup procedure is from 2009.
    We have official documentation that we keep up to date. The Fast-Start Failover part:
    https://docs.oracle.com/en/database/oracle/oracle-database/19/dgbkr/using-data-guard-broker-to-manage-switchovers-failovers.html#GUID-D26D79F2-0093-4C0E-98CD-224A5C8CBFA4
    and the Best Practices guide:
    https://docs.oracle.com/en/database/oracle/oracle-database/19/haovw/oracle-data-guard-best-practices.html#GUID-C3A78B07-6584-4380-8D53-E5B831A5894C
  2. The part about cascading standbys references a step-by-step guide from an external blog written many years ago for 11gR2.
  3. The DBMS_SERVICE doc is from 12cR1, while other links are from 21c doc or 19c doc. As of today, most implement 19c. That’s probably the version to use.
    https://docs.oracle.com/en/database/oracle/oracle-database/19/arpls/DBMS_SERVICE.html#GUID-C11449DC-EEDE-4BB8-9D2C-0A45198C1928
  4. The steps used to create the database service do not include any HA property, which will make most efforts useless. (see Table 153-6 in the link above).
  5. The article talks about TAF, but no steps exist to configure it. We don’t recommend TAF since 12c anyway. Today (19c), the recommendation is TAC (Transparent Application Continuity).
    https://www.oracle.com/docs/tech/application-checklist-for-continuous-availability-for-maa.pdf
  6. But, most important, TAF (or Oracle connectivity in general) does NOT require a host IP change! There is no need to change the DNS when using the recommended connection string with multiple address_lists.
  7. Some RedoRoutes examples are not correct. In this video I explain how they work and how to set them up:
    https://www.youtube.com/watch?v=huG8JPu_s4Q
  8. The diagram shows the master observer together with the standby database, which is a bad practice. I explain why and how here:
    https://www.youtube.com/watch?v=e81UPLfnLi0

The central message is:

If you need to implement a complex architecture using a software solution, pay attention that the practices suggested by the partner/integrator/3rd party match the ones from the software vendor. In the case of Oracle Data Guard, Oracle knows better 😉

Cheers

—

Ludovico

 

Video: Where should I put the Observer in a Fast-Start Failover configuration?

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The video explains best practices and different failure scenarios for different observer placements. It also shows how to configure high availability for the observer.

Here’s the summary:

  • Always try to put the observer(s) on an external site.
  • If you don’t have any, put it where the primary database is, and have one ready on the secondary site after the role transition.
  • Don’t put the observer together with the standby database!
  • Configure multiple observers for high availability, and use the PreferredObserverHosts Data Guard member property to ensure you never run the observer where the standby database is.

 

Far Sync and Fast-Start Failover Protection modes

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Oracle advertises Far Sync as a solution for “Zero Data Loss at any distance”. This is because the primary sends its redo stream synchronously to the Far Sync, which relays it to the remote physical standby.

There are many reasons why Far Sync is an optimal solution for this use case, but that’s not the topic of this post 🙂

Some customers ask: Can I configure Far Sync to receive the redo stream asynchronously?

Although a direct standby receiving asynchronously would be a better idea, Far Sync can receive asynchronously as well.

And one reason might be to send asynchronously to one Far Sync member that redistributes locally to many standbys.

It is very simple to achieve: just changing the RedoRoutes property on the primary.

This will work seamlessly. The v$dataguard_process will show the async transport process:

 

What about Fast-Start Failover?

Up to and including 19c, ASYNC transport to Far Sync will not work with Fast-Start Failover (FSFO).

ASYNC redo transport mandates Maximum Performance protection mode, and FSFO supports that in conjunction with Far Sync only starting with 21c.

Before 21c, trying to enable FSFO with a Far Sync will fail with:

So if you want FSFO with Far Sync in 19c, it has to be MaxAvailability (and SYNC redo transport to the FarSync).


If you don’t need FSFO, as we have seen, there is no problem. The only protection mode that will not work with Far Sync is Maximum Protection:

If FSFO is required, and you want Maximum Performance before 21c, or Maximum Protection, you have to remove Far Sync from the redo route.

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Ludovico

Can a physical standby database receive the redo SYNC if the Far Sync instance fails?

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The answer is YES.

In the following configuration, cdgsima_lhr1pq (primary) sends synchronously to cdgsima_farsync1 (far sync), which forwards the redo stream asynchronously to cdgsima_lhr1bm (physical standby):

But if cdgsima_farsync1 is not available, I want the primary to send synchronously to the physical standby database. I accept a performance penalty, but I do not want to compromise my data protection.

I just need to set up the Redoroutes as follows:

This is defined the second part of the RedoRoutes rules:

Let’s test. If I shutdown abort the farsync instance:

I can see the new SYNC destination being open almost instantaneously (because the old destination fails immediately with ORA-03113):

Indeed, I can see the new NSS process (synchronous redo transport) spawn at that time:

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Ludo

Can I rename a PDB in a Data Guard configuration?

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Someone asked me this question recently.

The answer is: yes!

Let’s see it in action.

On the primary I have:

And of course the same PDBs on the standby:

Let’s change the PDB RED name to TOBY: The PDB rename operation is straightforward (but it requires a brief downtime). To be done on the primary:

On the standby, I can see that the PDB changed its name:

The PDB name change is propagated transparently with the redo apply.

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Ludo

rhpctl addnode gihome: specify HUB or LEAF when adding new nodes to a Flex Cluster

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I have a customer trying to add a new node to a cluster using Fleet Patching and Provisioning.

The error in the command output is not very friendly:

The “RHPHELP_preNodeAddVal” might already give an idea of the cause: something related to the “cluvfy stage -pre nodeadd” evaluation that we normally do when adding a node by hand. FPP does not really run cluvfy, but it calls the same primitives cluvfy is based on.

In FPP, when the error does not give any useful information, this is the flow to follow:

  • use “rhpctl query audit” to get the date and time of the failing operation
  • open the “rhpserver.log.0” and look for the operation log in that time frame
  • get the UID of the operation e.g., in the following line it is “1556344143”:

  • Isolate the log for the operation: grep $UID rhpserver.log.0 > $UID.log
  • Locate the trace file of the rhphelper remote execution:

  • Find the root cause in the rhphelper trace:

In this case, the target cluster is a Flex Cluster, so the command must be run specifying the node_role.

The documentation is not clear (we will fix it soon):

node_role must be specified for Flex Clusters, and it must be either HUB or LEAF.

After using the correct command line, the command succeeded.

HTH

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Ludovico

Changing FPP temporary directory (/tmp in noexec and other issues)

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When using FPP, you might experience the following error (PRVF-7546):

This is often related to the filesystem /tmp that has the “noexec” option:

Although it is tempting to just remount the filesystem with “exec”, you might be in this situation because your systems are configured to adhere to the STIG recommendations:

The noexec option must be added to the /tmp partition (https://www.stigviewer.com/stig/red_hat_enterprise_linux_6/2016-12-16/finding/V-57569)

FPP 19.9 contains fix 30885598 that allows specifying the temporary location for FPP operations:

After that, the operation should run smoothly:

HTH

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Ludo

Why do PMs ask you to open Service Requests for almost EVERYTHING?

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If you attend Oracle-related events or if you are active on Twitter or other social medias used by technologists, you might know many of us Product Managers directly. If it is the case, you know that we are in general very easy to reach and always happy to help.

When you contact us directly, however, sometimes we answer “Please open a SR for that“. Somehow irritating, huh? “We had chats and drinks together at conferences and now this bureaucracy?” This is understandable. Who likes opening SRs after all? Isn’t just easier to forward that e-mail internally and get the answer first hand?

This is something that happened to me as well in the past when I was not working for Oracle yet, and that still happens with me now (the answer coming from me, as PM).

Why? The first answer is “it depends on the question“. If it is anything that we can answer directly, we will probably do it.

It might be a question about a specific feature: “Does product X support Y?”, “can you add this feature in your product?” or a known problem for which the PM already knows the bug (in that case is just a matter of looking up the bug number), or anything that is relatively easy to answer: “What are the best practices for X?”, “Do you have a paper explaining that?”, “Does this bug have a fix already?”

But there is a plethora of questions for which we need more information.

“I try this, but it does not work“. “I get this error and I think it is a bug“. “I have THIS performance problem“.

This is when I’d personally ask to open a SR most of the times (unless I have a quick answer to give). And there are a few reasons:

Data protection

Oracle takes data protection very seriously. Oracle employees are trained to deal with potentially sensitive data and cannot forward customer information via e-mail. That could be exposed or forwarded to the wrong recipients by mistake, etc. We don’t ask for TFA collections or logs via e-mail (even if sometimes customers send them to us anyway…).

There are special privileges required to access customer SRs, that’s the only secure way we provide to transfer logs and protected information. The files uploaded into the SRs must be accessed through a specific application. All the checkouts and downloads are tracked. When we need to forward customer information internally, we just specify the SR number and let our colleagues access the information themselves. Sometimes we use SRs just as placeholder to exchange data with customers, without having a support engineer working on it.

This is the single most important point that somehow makes the other points irrelevant. But still the remaining ones are good points.

Important pieces in the discussion do not get lost

The answer does not always come from first-hand… it might take 3-4 hops (sometimes more) and analysis, comments, explanations, discussions.

E-mail is not a good tool for this. Long threads can split and include just part of the audience (the “don’t reply to all” effect). Attachments are deleted when replying instead of forwarding… and pieces get lost.

This is where you would use a Jira, or a trouble ticketing system. Guess which is the one that Oracle uses for its customers? 🙂

MOS has internal views to dig into TFA logs (that’s why it is a good idea to provide one, whenever it might be relevant), and all the attachments, comments and internal discussions are centralized there. But we need a SR to add information to!

Win-win: knowledge base, feedback, continuous improvement

If you discover something new from a technical discussion, what do you do? Do you share it or do you keep it for yourself? MOS is part of our knowledge base and it is a good idea to store important discussions in it. Support engineers can find solutions in SRs with similar cases. It is a good opportunity for the support engineer him/herself to be involved in one more interesting discussion, so next time he/she might have the answer on top of the fingers.

To conclude, think about it as a win-win. You give us interesting problems that might help improving the product, and you get a Guardian Angel on your SR for free 😉

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Ludo

Oracle Fleet Patching and Provisioning (FPP): My new role as PM and a brand new series of blog posts

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It’s been 6 years since I’ve tried FPP for the first time (formerly Rapid Home Provisioning, or RHP).

Rapid Home Provisioning

FPP was still young and lacking many features at that time, but it already changed the way I’ve worked during the next years. I embraced the out of place patching, developed some basic scripts to install Oracle Homes, and sought automation and standardization at all costs:

Oracle Home Management – part 7: Putting all together

When 18c came with the FPP local-mode automaton, I have implemented it for the Grid Infrastructure patching strategy at CERN:

Oracle Grid Infrastructure 18c patching part 3: Executing out-of-place patching with the local-mode automaton

And discovered that meanwhile, FPP did giant steps, with many new features and fixes for quite a few usability and performance problems.

Last year, when joining the Oracle Database High Availability (HA), Scalability, and Maximum Availability Architecture (MAA) Product Management Team at Oracle, I took (among others) the Product Manager role for FPP.

Becoming an Oracle employee after 20 years of working with Oracle technology is a big leap. It allows me to understand how big the company is, and how collaborative and friendly the Oracle employees are (Yes, I was used to marketing nonsense, insisting salesmen, and unfriendly license auditors. This is slowly changing with Oracle embracing the Cloud, but it is still a fresh wound for many customers. Expect this to change even more! Regarding me… I’ll be the same I’ve always been 🙂 ).

Now I have daily meetings with big customers (bigger than the ones I have ever had in the past), development teams, other product managers, Oracle consultants, and community experts. My primary goal is to make the product better, increasing its adoption, and helping customers having the best experience with it. This includes testing the product myself, writing specs, presentations, videos, collecting feedback from the customers, tracking bugs, and manage escalations.

I am a Product Manager for other products as well, but I have to admit that FPP is the product that takes most of my Product Manager time. Why?

I will give a few reasons in my next blog post(s).

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Ludo