ZDLRA Internals, INDEX_BACKUP task in details

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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ZDLRA Internals, Tables and Storage

ZDLRA tables are owned by rasys user and are one extension of rman recovery catalog views. The internal tables that were added are just a few, but are important to understand how tasks works (mainly INDEX_BACKUP). In this post, I will show tables like plans, plans_details, blocks, and chunks. And besides that, show a little glimpse about how the files are stored.

Extra tables

If you check, officially, the rman recovery catalog already includes some columns from ZDLRA, the column VB_KEY identify the virtual backup key inside ZDLRA. It exists in RC_BACKUP_PIECE as an example. The extra tables added are linked with SBT tasks (clone to tape or cloud), replication (to other ZDLRA), storage (chunks), vbdf and plans (virtual full backup).

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ZDLRA, Virtual Full Backup and Incremental Forever

One of the most knows features of ZDLRA is the virtual full backup, basically incremental forever strategy. But what this means in real life? In this post, I will show some details about that and how interesting they are, check what it is Virtual Full Backup and Incremental Forever strategy for ZDLRA.

This post is based on my previous one where I showed all the steps to configure the VPC and enroll database at ZDLRA. 

Virtual Full Backup

A virtual full backup appears as an incremental level 0 backup in the recovery catalog. From the user’s perspective, a virtual full backup is indistinguishable from a non-virtual full backup. Using virtual backups, Recovery Appliance provides the protection of frequent level 0 backups with only the cost of frequent level 1 backups.

This definition (and image) are in the Zero Data Loss Recovery Appliance Administrator’s Guide and I think that represents the essence of the virtual full backup. ZDLRA receive the incremental level 1 backup, index it, and generate a level 0 to you that it is indistinguishable from a normal backup level 0.

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How to use ZDLRA and enroll a database

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

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

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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Reimage ODA

The idea to reimage ODA is to refresh the environment without the need to jump from one by one to reach the last available version, or even rescue the system from S.O. failure/crash. The process to do a reimage can be check in the official documentation but unfortunately can be very tricky because the information (the order and steps) are not 100% clear. The idea is to show you how to reimage using version 18 (18.3 in this example), that represents the last available.

In resume the process is executed in the order:

  1. ILOM: Boot the ISO
  2. Prepare to create the appliance
  3. Upload GI and DB base version to the repository
  4. Linux: Create the appliance
  5. Firmware and patch
  6. Create Oracle Homes and the databases
  7. Finish and clean the install

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RMAN, Allocate channel, CDB, and CLOSE: bug

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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Shrink ASM Diskgroup and Exadata Grid Disks

Here I will cover the shrink of ASM diskgroup in Exadata environment running VM’s. The process here is the opposite of what I wrote in the previous post, but have a tricky part that demands attention to avoid errors. The same points that you checked for extending are valid now: number the cells, disks per cell, ASM mirroring, and the VM that you want to change continue to be important, but we have more now. Besides that, the post shows how to verify (and “fix”) if you have something in the ASM internal extent map that can block the shrink.

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Increase size for Exadata Grid Disks

A quick article about a maintenance task for Oracle Exadata when you are using OVM and you divided your storage cell disks for every VM. Here I will show you how to extend your Grid Disks to add more space in your ASM diskgroup.

The first thing is being aware of your environment, before everything you need to know the points below because, they are important to calculate the new space, and to avoid do something wrong:

  • Number of cells in your appliance.
  • Number of disks for each cell.
  • Mirroring for your ASM.
  • The VM that you want to add the space.

The “normal” Exadata storage cell has 12 disks, the Extreme Flash version uses 8 disks per storage. If you have doubt about how many disks you have per storage cell, you can connect in each one and check the number of celldisks you have. And before continuing, be aware of Exadata disk division:

To do this change we execute three major steps: ASM, Exadata Storage, and ASM again.

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