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12c Release 1

Creating a RAC 12.1 Data Guard Physical Standby environment (4)

In the previous three parts of this series a lot of preparation work, needed for the configuration of Data Guard, was performed. In this part of the mini-series they all come to fruition. Using the Data Guard broker a switchover operation will be performed. A couple of new features in 12c make this easier. According to the “Changes in This Release for Oracle Data Guard Concepts and Administration” chapter of the 12.1 Data Guard Concepts and Administration guide:

When [you, ed.] perform a switchover from an Oracle RAC primary database to a physical standby database, it is no longer necessary to shut down all but one primary database instance.

I have always wanted to test that in a quiet moment…

Creating a RAC 12.1 Data Guard Physical Standby environment (3)

In the previous two parts of this series you read about my lab environment and the preparations on the network side as well as the database. In this part I’ll cover the database duplication. Again, this won’t be a short post …

NOTE: As always, this is just a demonstration using VMs in my lab, based on my notes. Your system is most likely different, so in real-life you might take a different approach. The techniques I am using here were suitable for me, and my own small scale testing. I tried to make sure they are valid, but you may want to allocate more resources in your environment. Test, test, test on your own environment on test kit first!

Step 1: Create an initialisation file

The next step is the preparation of an initialisation file. I am taking NCDBA as the sample and transfer it over to rac12sec1:

Creating a RAC 12.1 Data Guard Physical Standby environment (2)

In the first part of this mini-series you saw me define the environment as well as creating a primary database. With that out of the way it’s time to think about the standby. Before the standby can be created, a few preparations are necessary both on the primary as well as the standby cluster.

NOTE: As always, this is just a demonstration using VMs in my lab, based on my notes. Your system is most likely different, so in real-life you might take a different approach. The techniques I am using here were suitable for me, and my own small scale testing. I tried to make sure they are valid, but you may want to allocate more resources in your environment. Test, test, test on your own environment on test kit first!

Preparing the Creation of the Standby Database

Creating a RAC 12.1 Data Guard Physical Standby environment (1)

I have just realised that the number of posts about RAC 12c Release 1 on this blog is rather too small. And since I’m a great fan of RAC this has to change :) In this mini-series I am going to share my notes about creating a Data Guard setup on my 2 node 12.1.0.2.161018 RAC primary + identical 2 node RAC standby system in the lab.

NOTE: As always, this is just a demonstration using VMs in my lab, based on my notes. Your system is most likely different, so in real-life you might take a different approach. The techniques I am using here were suitable for me, and my own small scale testing. I tried to make sure they are valid, but you may want to allocate more resources in your environment. Test, test, test on your own environment on test kit first!

The lab Environment

My environment consists of the following entities:

GTT and Smart Scan – the importance of the append hint

While writing the previous two posts about GTTs and Smart Scan, I stumbled across an interesting observation. When I started putting my thoughts to (virtual) paper, I thought it was going to be a short post. Well, it wasn’t to be, again. Anyway, you might find this interesting.

Initial Situation

If you read the previous posts this code example I used to populate the GTT might look familiar:

insert /*+ append */ into gtt select * from t4 where rownum < 400000;
 
commit;

In situations like this where I’m moving data I developed a habit of using the append hint. I guess I’ve been working on HCC tables a bit too much and therefore didn’t even make a conscious decision to use that hint. It was the right thing to do, as you will see next.

The full test harness is shown here again for reference:

Smart Scanning GTTs – what about Flash Cache?

Continuing the example of the previous blog post (is it possible to Smart Scan GTTs?), I am investigating if Smart Scans against GTTs can benefit from Flash Cache, or “optimised reads”. The easiest way to see this in your session is to calculate the change in session counters based on v$mystat or v$sesstat. Other tools might also provide information about the amount of data read from Flash Cache, but there are quite often extra licenses required …

Little things worth knowing: Can I Smart Scan a Global Temporary Table?

A question that has come up while preparing to deliver another Exadata Optimisation Class is whether you can offload queries against Global Temporary Tables (GTT) or not. There are subtle differences between heap tables and GTTs such as how statistics are handled and where they are stored that merit a little investigation.

I have used the lab environment on the X3-2 (Exadata 12.1.2.3.0, 12.1.0.2.160419 RDBMS) to test if I can Smart Scan GTTs. There are some enhancements in 12c regarding GTTs that are mentioned on the Optimiser blog here:

https://blogs.oracle.com/optimizer/entry/gtts_and_upgrading_to_oracle

The Setup

Building an RPM for the Oracle database on Oracle Linux 7

Thinking about automation a lot, especially in the context of cloud computing, I have decided to create a small series of related posts that hopefully help someone deploying environments in a fully automated way. As my colleague @fritshoogland has said many times: the only way to deploy database servers (or any other server for that matter) in a consistent way, is to do it via software. No matter how hard you try to set up 10 identical systems manually, there will be some, maybe ever so subtle, differences between them. And with the cloud you probably have 42 systems or more to deal with! In this context, my first post could be a building block: the provisioning of the Oracle RDBMS the form of an RPM.

The idea

In a nutshell, I would like to

Little things worth knowing: when a transient ASM disk failure cannot be fixed in time

In the previous blog post I used libvirt and KVM in my lab environment to simulate a transient disk failure and how to recover from it. This post takes this example a step further: I am simulating another disk failure, but this time won’t pretend I can fix the issue and put it back. In other words, I simulate the effect of the disk_repair_time hitting zero.

Most of what I am covering here is an extension of the previous post, I’ll mention the main detail here for your benefit, but would like to invite you to revert to the previous post for more detail.

The idea is to show you the output of the ASM alert.log and result of the lost disk in the V$-views.

As with the previous post, the code examples in this one are for demonstration purposes only!

Little things worth knowing: transient ASM disk failures in 12c

For quite some time we have been treated nicely by ASM when it comes to transient disk failures. Since 11.1 (if memory serves me right), transient failures won’t cause an ASM disk to be dropped immediately. This is good, because it can potentially save a lot of time! When a disk is dropped from an ASM disk, a rebalance operation is unavoidable. And there is more than a chance of another one following it, because ultimately you want to add the disk back to the disk group. Well, to be fair, this is only applicable for normal or high redundancy disk groups.

The feature I just described very briefly is referred to as ASM Fast Mirror Resync, and documented in the ASM Administrator’s Guide in section Administering Oracle ASM Disk Groups.