The Gold architecture for MAA is used to emphasis the application continuity. All the possible outages (planned or no) are protected by Oracle features. Here we are one step further and start to design using multi-site architecture. Data Guard, RAC, Oracle Clusterware, everything is there. But even with these, ZDLRA is still needed to allow complete protection.
With the MAA references, we have the blueprints and highlights how to protect them since the standalone/single instance until the multiple site database. But for Gold we are beyond RPO and RTO, they are important but application continuity and data continuity join to complete the whole picture.
Oracle Data Guard Broker allows the database administrators to automate some tasks and an easy way to configure properly a lot of features and details for data guard environments. The Fast-Start FailOver (FSFO) allows the broker to automatically failover to standby database in case of failure of the primary. But until 19c the only option is always to trigger the failover. This changed at 19c with a nice new feature that allows us to put FSFO in Observe-Only Mode.
In this post, I will focus just on new features for FSFO like Observer-Only Mode and Health Conditions for it. Lag and other details will not be covered here.
The Observe-Only Mode is a simple change that allows putting the FSFO to just observing/monitoring the DG environment, but in case of failure, it does not change the roles between primary and standby. Simple like that. As the Broker documentation for Observe-Only Mode says:
The observe-only mode enables you to test the impact of using fast-start failover in your configuration, without making any actual changes to the configuration.
This article closes the series for DG and Fast-Start Failover that I covered with more details the case of isolation can leverage the shutdown of your healthy/running primary database. The “ORA-16830: primary isolated from fast-start failover partners”.
In the first article, I wrote about how one simple detail that impacts dramatically the reliability of your MAA environment. Where you put your Observer in DG environment (when Fast-Start Failover is in use) have a core figure in case of outages, and you can face Primary isolation and shutdown. Besides that, there is no clear documentation to base yourself on “pros and cons” to define the correct place for Observer. You read more in my article here.
In the second article, I wrote about one new feature that can help to have more protected and cover more scenarios for Fast-Start Failover/DG. Using Multiple Observers you can remove the single point of failure and allow you to put one Observer in each side of your environment (primary, standby, and a third one). You can read more in my article here.
In this last article, I discuss how, even using all the features, there is no perfect solution. Another point is discussing here is how (maybe) Oracle can improve that. Below I will show more details that even multiple observers continue to shutdown a healthy primary database. Unfortunately, it is a lot of tech info and is a log thread output. But you can jump directly to the end to see the discussion about how this can be improved.
Recently I made a post about a little issue that I got with Oracle Data Guard. In that scenario, because of outage in the standby datacenter, healthy primary database shutdown with error “ORA-16830: primary isolated…”. Just to remember that the database was running with Maximum Availability, Fail-Start Failover enabled, and (the most important detail) the Observer was running in the standby datacenter too.
The point from my previous post tried to show that does not exists one doc that provides full details about “pros” and “cons” where put your observer. Whatever the place, on the primary datacenter or in standby, it has little details to check. Even the best (ideal) scenario, with a third datacenter, can be tough to sustain.
Here I will try to show one option that can help you and improve the reliability of your MAA/DG environment. At least, you will have more options to decide how to protect your database. Bellow, I show some details about how to configure and use multiple observers, but if you want to jump and see a little concern you can directly to the end of the post.
Some months ago I got one error with Oracle Data Guard and now I had time to review it again and write this article. Just to be clear since the beginning, the discussion here is not about the error itself, but about the circumstances that generated it.
The environment described here follows, at least, the most common best practices for DG by Oracle. Have 1 dedicated server for each one: Primary Database, Physical Standby Database, and Observer. The primary and standby reside in different data centers in different cities, dedicated network for interconnecting between sites, protection mode was Maximum Availability, and runs with Fast-Start Failover enabled (with 30 seconds for threshold). The version here is 12.2 but will be the same for 19c. So, nothing so bad in the environment, basic DG configuration trying to follow the best practices.
Neste penúltimo da série sobre MAA com Oracle RAC 11GR2 vou falar um pouco sobre como ocorre o failover automático em caso de falha do primary. Vou demonstrar que basicamente você não faz nada, todo o trabalho “sujo” será pelo próprio Oracle.
Este artigo irá mostrar como o MAA resolve de forma automática todos os pontos de um failover. Claro que para isso você tem que ter tudo devidamente configurado e operacional. Você vai precisar de um Observer configurado e o Fast-Start Failover habilitado (como demonstrado aqui) bem como um Broker operacional (veja aqui). Se você leu os artigos anteriores você já tem tudo isso configurado e não irá se preocupar com mais nada.
Até o momento você tem um banco de dados primary (maa) e um banco de dados standby (maastb) sincronizados em Maximum Availability (com Real-Time no envio de redo). Além disso o Fast-Start Failover está habilitado.
Já aviso que o artigo pode ser extenso devido aos logs, tentarei suprimir as informações que não são necessárias. Mas mesmo assim recomendo a leitura para compreender tudo o que ocorre.
Depois de configurar o Broker, precisamos de um último passo para garantir que os requisitos básicos do MAA estejam contemplados. Nos últimos artigos passamos por alguns passos que provavelmente você não iria realizar em produção (e nem gostaria), fizemos o failover e o switchover (ambos com o broker – que configuramos aqui).
Neste artigo vamos configurar/adicionar ao ambiente a figura do Observer, será habilitado o Fast-Start Failover (FSFO) no Broker para permitir um monitoramento em tempo real do ambiente. Com isso, em uma eventual falha do ambiente primary o standby irá assumir o papel sem ser necessário executar qualquer comando.