Tag Archives: Database

ZDLRA, Real-Time Redo and Zero RPO

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The idea for Real-Time Redo is to reach zero RPO for every kind of database and this includes ones with and without DG. As you can see in my last post, where I showed how to configure Real-Time Redo for one database, some little steps need to be executed and they are pretty similar than a remote destination for archivelog for DG.

But if you noticed, the configuration for the remote destination was defined as ASYNC, and hinted like that at ZDLRA docs (“Protection of Ongoing Transactions” or at “How Real-Time Redo Transport Works”). In the same post, I suggested as “controversial” because the ASYNC does not guarantee the RPO zero. 

You can see more in the DataGuard docs at (Oracle Data Guard Protection Modes and Oracle Data Guard Concepts and Administration), but the resume it is:

  • ASYNC: The primary database does not wait for the response from a remote destination.
  • SYNC/NOAFIRM: The Primary database holds commit until the remote destination report that received the redo data. It does not wait until the remote site report that wrote the data in the disc.
  • SYNC/AFFIRM: The primary database holds commit until the remote destination report that received redo data and wrote it at the disk.

You can read with more details the difference here: Best Practices for Synchronous Redo Transport and Best Practices for Asynchronous Redo Transport.

The idea is simple, if you use ASYNC, there is no guarantee for zero data loss between the primary database and the remote destination.

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ZDLRA Internals, Virtual Full Backup

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Virtual Full Backup probably is the most know feature of Oracle Zero Data Loss Recovery Appliance (ZDLRA) and you can check here how it works. In this post I will show how virtual full backup works internally and integrate INDEX_BACKUP task with tables like PLANS, PLAN_DETAILS, CHUNKS, and BLOCKS.

About the internal tables, you can check my previous post “ZDLRA Internals, Tables and Storage” where I explained details about that. To understand the INDEX_BACKUP task, check my post “ZDLRA Internals, INDEX_BACKUP task in details”. But if you know nothing and want to start reading about ZDLRA, you can check my post “Understanding ZDLRA” and check all the features and details.

The base for this article is virtual full backup and incremental forever strategy. I explained both at “ZDLRA, Virtual Full Backup and Incremental Forever” and I included hot it’s work integrated with rman backup. Basically, after an initial backup level 0, you execute just level 1 backups and ZDLRA generated a virtual backup level 0. But here, in this post, I will show you how it works in some internal details.

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ZDLRA, 19.2

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Last week, at 27/August/2019, ZDLRA team released the new major version 19.2 (19.2.1.1.1) of Recovery Appliance Software. As always, some new features like supported databases, but some downsides too.

The main features for the software side:

  • Support for 19c databases.
  • Improved way to apply the patch (the rpm installation is not anymore manual).
  • Improved way to rollback the patch in some cases.

Other changes that deserve the hint:

  • Runs over 19.4 version of GRID and RDBMS.
  • Runs over Exadata System Software 19.2.3.0.0 (this means OEL 7) for DB and Storage.
  • Updated version for TFA, Exachk, and OEDA; all 19.x version.

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ZDLRA Internals, INDEX_BACKUP task in details

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For ZDLRA, the task type INDEX_BACKUP it is important (if it is not the most) because it is responsible to create the virtual full backup. This task runs for every backup that you ingest at ZDLRA and here, I will show with more details what occurs at ZDLRA: internals steps, phases, and tables involved.

I recommend that you check my previous post about ZDLRA: ZDLRA Internals, Tables and Storage, ZDLRA, Virtual Full Backup and Incremental Forever, and Understanding ZDLRA. They provide a good base to understand some aspects of ZDLRA architecture and features.

Backup

As you saw in my previous post, ZDLRA opens every backup that you sent and read every block of it to generate one new virtual full backup. And this backup is validated block a block (physically and logically) against corruption. It differs from a snapshot because it is content-aware (in this case it is proprietary Oracle datafile blocks inside another proprietary Oracle rman block) and Oracle it is the only that can do this guaranteeing that result is valid.

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How to use ZDLRA and enroll a database

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ZDLRA it is an Oracle dedicate appliance specialized to manage your backups, but more than that, provide you zero data loss. I already made an introduction about ZDLRA in my previous post and here I will show how to use and enrolling protected database at ZDLRA: enroll database, create policies and access with rman. Understand how to use ZDLRA, at least the starting point.

Every project starts with scope definition, steps, and requirements. It is not different for ZDLRA project, it is a big appliance, expensive, and integrate a lot of things in just one place: backups, archivelogs, redo, replication, and RPO. The requirements vary from project to project, I will not discuss that here. But will show you the tech part about the usage.

The post has two divisions, the first it is the technical part. You can check how to do that. The second contains the information/documentation part, where I will show more details about the steps.

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Understanding ZDLRA

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Oracle Zero Data Loss Recovery Appliance (ZDLRA) deliver to you the capacity to improve the reliability of your environment in more than one way. You can improve the RPO (Recovery Point Objective) for your databases until you reach zero, zero data loss. And besides that, adding a lot of new cool features (virtual backups, real-time redo, tape and cloud, DG/MAA integration) on the way how you do that your backups (incremental forever), and backup strategy. And again, besides that, improve the MAA at the highest level that you can hit.

But this is just marketing, right? No, really, works pretty well! My history with ZDLRA  starts with Oracle Open World 2014 when they released the ZDLRA and I watched the session/presentation. At that moment I figure out how good the solution was. In that moment, hit exactly the problem that I was suffering for databases: deduplication (bad dedup). One year later, in 2015 at OOW I made the presentation for a big project that I coordinate (from definition implementation, and usage)  with 2 Sites + 2 ZDLRA + N Exadata’s + Zero RPO and RTO + DG + Replication. And at the end of 2017 moved to a new continent, but still involved with MAA and ZDLRA until today.

This post is just a little start point about ZDLRA, I will do a quick review about some key points but will write about each one (with examples) in several other dedicates posts. I will not cover the bureaucratic steps to build the project like that, POC, scope definition, key turn points, and budget. I will talk technically about ZDLRA.

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INDEX_BACKUP task for ZDLRA, Check percentage done

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Quick post how to check and identify done for INDEX_BACKUP task in ZDLRA. In one simple way, just to contextualize, INDEX_BACKUP is one task for ZDLRA that (after you input the backup of datafile) generate an index of the blocks and create the virtual backup for you.

Here I will start a new series about ZDLRA with some hints based on my usage experience (practically since the release in 2014). The post from today is just little scratch about ZDLRA internals, I will extend this post in others (and future posts), stay tuned.

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RMAN, Allocate channel, CDB, and CLOSE: bug

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Allocate channel for RMAN is used in various scenarios, most of the time is useful when you use tape as device type or you need to use some kind of format. The way to do the allocation not changed since a long time ago, but when you run the database in container mode you can hit a bug that turns your channel unusable. I will show you the bug and how to avoid it with a simple trick.

This bug hit every version since 12 and I discovered it last year when testing some scenarios, but I was able to test and post just recently. It just occurs for CDB databases and exists just one one-off solution published for 12.2. But there is one workaround more useful and works for every version.

The most interesting part is that everything that we made until now when allocate channel will not work. You can search in all doc available for allocate channel since 9i until 19c the first thing that you made after open the run{} is allocate channel. This is the default and recommended in the docs: for 19c, 18c, and 9i.

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Observer, Quorum

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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.

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Exadata X8, Second look

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Every year Oracle arrives and release new version of Exadata with a plenty of new things. We have the natural evolution from hardware (more memory, more cpu…) and sometimes news features from software side. The point for this post today it is not about the HW and SW things, but something is hidden in the small lines of the new X8.

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