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Oracle Disaster Recovery in the cloud – Part 2: Getting started on Amazon Web Services

We'll create both primary and standby database servers in AWS using Oracle Linux EC2 instances, running Oracle Database 11g Release 2 SE with Standby™.

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Oracle DR in AWS Cloud
By IT Manager
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October 24, 2019
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Part 2: Getting started on Amazon Web Services

This post is a follow on from the “Oracle Disaster Recovery in the Cloud – Part 1”.

In this post I will be showing you an example where I will create both primary and standby database servers in AWS using Oracle Linux EC2 instances running Oracle Database 11g Release 2 Standard Edition One with Standby for standby management. As mentioned in part 1, there is more than one way to go about getting an environment built in the Amazon cloud. You can use a few EC2 instances using public IP addresses which make use of Elastic IPs, or you can look at using a more private isolated environment using Amazon Virtual Private Cloud (VPC) with more flexibility using your own network address range - in effect, creating your own little private network in the cloud. For more details on VPC please follow this link. As with most things in IT, I always recommend starting simple, keeping it basic, then once you are more familiar with the technologies and options you can expand from there and make things more complex.

Once you have created your AWS account login, navigate to the “AWS Management Console”. The Console will load and you will see the extensive range of Amazon Web Services available to you. I do encourage you to read up about some of these services as many are truly useful and may suit your needs and requirements. I will focus on the EC2 service in this post. When you select the “EC2 (Servers in the cloud)” option you will be presented with the Amazon EC2 Console Dashboard.

aws-ec2-dashboard-300x149

Amazon EC2 Dashboard Example

I found that the dashboard is easy to use and navigate. It is important to note that when talking about “Instances” when working with the EC2 dashboard, we are talking about Virtual Machines.

Now the overall structure we are going to build is the following:

  • Oracle Linux 5 EC2 instance running our primary database (11g)
  • Oracle Linux 5 EC2 instance running our standby database (11g)
  • 2 Elastic IP addresses will be created and one will be assigned to the primary node and the second to the standby node.
  • 1 Security Group will be created. This can be seen as your firewall for your instances.
  • 1 Key Pair will be created. This will be used when establishing SSH connections to your instances.

One of the great things about AWS is that there are a large number of “pre created” machine images, referred to as Amazon Machine Images (AMI), available to make it easy for you to quickly establish a new environment.  For more details about these images see https://aws.amazon.com/amis.

In the next section I will provide you with the high level steps you need to follow to establish an environment running Standby managing an Oracle 11g Standard Edition One standby database environment using Amazon EC2.

Summarized Steps

The Steps can be summarized as follows:

  • From the EC2 Dashboard select the Region on the top right hand side.  In my steps below I used US East (N. Virginia). I will be using this region for both the primary and standby servers.
  • The second step is to create a Key Pair, this can be done by selecting “Key Pairs” from the Navigation on the left side. Once selected click on “Create Key Pair” and follow the instructions.
  • The next step is creating a new security group. This is optional. You can use the default one available. Just make sure that for your security group, that SSH (port 22) and HTTPS port 8443 used by Standby GUI is added to the Inbound Rules. If you want to allow other ports such as the default listener port 1521 you can add that here as well. Once you have made your rule changes, make sure you click on the “Apply Rule Changes” to save your settings.
  • The next step is to create the two Virtual Machines, or EC2 instances as it is known in AWS. As mentioned earlier there are a number of available machine images (AMI) that makes this step easy. First click on “Instances” in the left Navigation window.
  • From the main window click on “Launch Instance” (top left).
  • The “Create a New Instance” wizard will be launched. You can just select the default “Classic Wizard” and click on Continue.
  • You can now select the images you want, and in this post I want to make it quick and easy so I select the “Community AMIs” tab and search for “Oracle Database”. The search does take a little bit of time, but you will then be presented with a list of available images with Oracle Database software already installed. In my case I selected the Oracle Database 11.2.0.1 64bit Standard Edition One (ami-31739c58) AMI image.

aws-ami-300x195

  • The instance details page allows you to specify the number of instances and the instance type. I recommend starting with the High-CPU Medium (c1.medium) type to start off with. Please review pricing as you pay different hourly rates depending on the instance type you select.
  • I accepted the defaults under the “Advanced Instance options”, such as the default kernel id and ram disk id.
  • In the basic setup the default supplied storage is sufficient, but you can modify this to your requirements. I accepted the default and clicked on continue.
  • For the “Name” tag I supply the name I want to identify my instance as.  In this case I am using “dbvaws01” – primary and “dbvaws02” for the standby instance.
  • Under the Key Pairs I select the Key pair created earlier.
  • Under the Configure Firewall option I select the Security Group created earlier.
  • This will bring you to the “Review” screen from where you can get an overview of the instance you are about to create (Launch). Once happy just click on “Launch” and your instance will be created. This process does take a few minutes but you should see the instance now detailed in your “Instances” listing.
  • You can now create two new Elastic IP addresses. These can be created from the “Elastic IPs” under the left Navigation bar. Create two new addresses and associate each one to one of the Instances you have created. Also make note of these IP addresses and to which machine you assigned it.
  • Once the Instances are created, and the Elastic IP addresses are assigned, you can SSH to the machines using the key pair created earlier. For example my key is called aws_key.pem and I can establish the connection with this ssh command:
ssh –i aws_key.pem root@<elastic_IP_address_here>
  • On first login you will be asked if you want to create a database.  (Remember we selected our new instances to be built from AMI images with Oracle already installed). For the primary server (dbvaws01) I say Yes and create a new database called testdb. Provide the new SYS, SYSTEM, DBSNMP and SYSMAN user passwords as well as the Apex Admin password. Once the passwords are provided the database creation process will start. This step does take a few minutes to complete. Once the database creation is complete, the setup of the Secure Backup Cloud module will begin. I was not going to use it at this point so just canceled it (ctrl-c). On the second instance, which is the standby server (dbvaws02) I choose not to create a database.
  • Once the above steps are complete you should now have two Amazon EC2 instances running with one of these instances running your primary Oracle Database on it called testdb. Make sure you have a password assigned to the Oracle Unix account. It is also important to ensure that the local firewall (IPTables) on the Linux instances include rules to allow the port 8443 (used by the Standby GUI). This is only required if you have a firewall (iptables) configured. In my case iptables are not configured, so no need to change anything. In most of the default AMI images this is disabled and you can use your Amazon Security Groups assigned to the EC2 instances to handle firewall rules. But for more strict configurations using IPTables for added security is a good idea, but I will not go into that now.

Note: Remember that when you shutdown an EC2 instance, the Elastic IP address that was assigned to it will be removed, meaning it will lose its association with that particular instance.  When you just perform a restart (reboot) of the instance, it will not lose it.  So if you do shutdown your instances and start them up later, you will have to associate the Elastic IP addresses again.  There are a few other options available, for example when using a VPC (Virtual Private Cloud), but I will not go into that in this post.

We are now getting to the stage where you need to perform the pre-requisites for installing Standby.  I will cover 3 of these steps, which I think are important, and will make the installation process much easier going forward.

Now at this stage you should have two instances running, but they don’t know about each other, and you will notice that their default hostnames (run the “hostname” command from the command line) are made up of the internal DHCP IP address that is assigned. Something like this:
# hostname
ip-10-194-237-163

Before you install Standby there are still more steps to perform. Now as you have allocated two Elastic IP’s (EIPs) and assigned them to the primary and standby server, you can use the EIP’s public DNS name going forward which can be something like:  ec2-154-243-183-73.compute-1.amazonaws.com.  But to me this is not that user friendly.

I know there are more options, and you are welcome to investigate and use these. But for this demo install, to enable more user friendly names, I add two entries to my local /etc/hosts files on both systems, where I assign each of the EIPs to the hostnames I will be using.

For example I have 2 x EIP’s one assigned to the primary hostname and the second to the Standby hostname. So in my example I end up with these two entries in both my Instance’s /etc/hosts file (please note the IP’s below will need to be replaced with your Elastic IP’s, these are just examples).

154.243.183.95    dbvaws01
154.243.183.97    dbvaws02

Note: There are other options available, such as using DNS etc.  You are welcome to try these options out. To ensure that Standby is making use of these more meaningful names "dbvaws01" and "dbvaws02" we need to create what we call a hostname command script or HOSTNAME_CMD script.

This script is executed by Standby to get the correct hostname to use. This is used to bypass the default "hostname" but to use the one you would like to use. This name needs to be resolvable to an IP address. And in this case we have already added the two entries above to two instances' /etc/hosts files.

I now create a script in /usr/local/bin/ called "dbv_host" and make sure it is executable (chmod a+rx dbv_host). The only thing this script needs to do is echo back the hostname you would like to use for that server.

Examples below:

On the primary server which will be "dbvaws01" I have this:

[/usr/local/bin] # ls -al dbv_host
-rwxr-xr-x 1 root root 31 Oct 16 22:45 dbv_host
[/usr/local/bin] # cat dbv_host
#!/bin/bash
echo "dbvaws01"

On the standby server which will be "dbvaws02" I have this:

[/usr/local/bin] # ls -al dbv_host
-rwxr-xr-x 1 root root 31 Oct 16 22:45 dbv_host
[/usr/local/bin] # cat dbv_host
#!/bin/bash
echo "dbvaws02"

Now when you execute these scripts it just returns one line, which is the hostname you want to use. Example if executed on the primary I get the following:

[/usr/local/bin] # ./dbv_host
dbvaws01
[/usr/local/bin] #

Now it is important that once you have finished running the initial dbvisit setup process to create the DDC file you need to update the DDC file to make sure that the parameter HOSTNAME_CMD=/usr/local/bin/dbv_host Tip: Another thing you can do to make sure it is easy to see which system you are on is to update the root and oracle Unix account PROMPT, which can be achieved by modifying the PS1 environment variable to something like this:

PS1="`whoami`@`dbv_host`:[\$PWD] # "
export PS1

Once you have done this and either re-login or just run ". .bash_profile" while in the home folder and you will get the new prompt which I find much better. Example below I execute the bash_profile after I have edited it with "vi", and once the profile is loaded you can see the new prompt, I also updated the oracle environment so when logging in as oracle I get the more user friendly prompt:

root@ip-10-195-23-24:[/root]
$ . .bash_profile
root@dbvaws01:[/root] #
root@dbvaws01:[/root] # su - oracle
oracle@dbvaws01:[/home/oracle] #

Installing Standby - Pre-Requisites
Downloading and Installing Standby
  • Establishing SSH equivalence: This means you can establish ssh connections between the two systems as the “oracle” UNIX account without being prompted for passwords.  When using Oracle Linux this can easily be done with a few commands. Now, the default SSH configuration on the Amazon images are set to only allow key authentication with password authentication disabled. This can easily be modified in the /etc/ssh/sshd_config file by setting the "PasswordAuthentication yes" and restarting the ssh daemon (/etc/init.d/sshd restart), but when doing this you reduce the security so it is not recommended, but I do think it is worth mentioning the option.
  • If you do enable password authentication then you can easily use the ssh-keygen and ssh-copy-id commands to setup ssh equivalence, example run this command on both systems to generate your oracle unix account public and private keys:
# ssh-keygen –t dsa

When executing this command just accept the defaults and press enter; DO NOT enter a passphrase. Once this is done, run the following two commands (as the Oracle Unix account) on both systems, when asked to continue say “yes” and supply the oracle Unix account passwords when prompted:

# ssh-copy-id -i /home/oracle/.ssh/id_dsa.pub oracle@dbvaws01
# ssh-copy-id -i /home/oracle/.ssh/id_dsa.pub oracle@dbvaws02

Once you have executed the above you should be able to establish ssh connections between the two Instances without passwords. For example, if you execute these commands you should be able to connect without passwords.

## On Primary: 
ssh oracle@dbvaws02
## On Standby: 
ssh oracle@dbvaws01

As you can see it is nice and easy to do using these two commands, but it does require PasswordAuthentication to be enabled in SSH. There is another option, which is to manually copy the key details into the ~/.ssh/authorized_keys file and this process is explained in detail “here”.

The next step in preparing for the Standbyinstallation is creating the base Dbvisit software directory /usr/local/dbvisitand making sure that the Oracle Unix account is the owner. I know everyone prefers to install software into their own location, but I do recommend you make use of the default location of /usr/local/dbvisit. This can be done by doing the following as the root user:

mkdir /usr/local/dbvisit
chown oracle:oinstall /usr/local/dbvisit

One of the most important folders to create is the default ARCHDEST folder. This is the folder where the standby database will be storing the archive logs it is receiving from the primary. It is good practice to ensure that this folder exists on both the primary and standby servers and in the same location. In this example I am using /u01/app/oracle/archive/dbvisit/testdb.

In a real life production system you would put this folder on a filesystem where there is sufficient space and make sure the oracle software owner own this folder. Create this folder on both systems and when running the initial Standby setup configuration, make sure that you specify this folder for the ARCHDEST location.

You can now download and install the latest Standby software and install Standby using the standard installation procedures for Linux. This is a two step process:

1. First download the latest install file and copy it to both the Instances into a temporary folder. I always create a temporary folder in the /home/oracle folder with the version number. I then copy the downloaded zip file into this folder and perform the installation from there. Example:

/home/oracle/6.0.40/dbvisit-standby6.0.40_linux.zip

Now run the initial install on both systems.

cd /home/oracle/6.0.40
unzip dbvisit-standby6.0.40_linux.zip
tar xf dbvisit-standby6.0.40.tar
cd dbvisit
chmod 755 dbvisit_install
./dbvisit_install

2. The second step is to run the initial setup on the Primary server (dbvaws01). This can be done from the command line or via the GUI. From the command line all you need to do, on the primary server, is run as the Oracle Unix account the “dbvisit_setup” executable which will start the configuration process (which creates the Dbvisit Configuration file - DDC file). Example:

oracle@dbvaws01:[/home/oracle] # cd /usr/local/dbvisit/standby/
oracle@dbvaws01:[/usr/local/dbvisit/standby] # ./dbvisit_setup 

When asked if this is the primary server, say yes. And select menu option 1 to start the new configuration process. Important: Make sure you use “dbvaws01” and “dbvaws02” as the names for your primary and standby servers when asked by the setup wizard. For more details please see the online documentation here.

If you want to run the configuration via the GUI, you can access the primary server using your Elastic IP address that you assigned to the primary server. In this example the EIP that was assigned to the primary was 154.243.183.95. The URL to use the GUI would then be:

https:\\154.243.183.95:8443

For more details on the GUI setup please see here.

IMPORTANT: Once you have finished the Standby installation and configuration, make sure you set the HOSTNAME_CMD=/usr/local/bin/dbv_host in your created DDC configuration file. In this example my DDC file was created as /usr/local/dbvisit/standby/dbv_testdb.env

You can use the Standby built-in feature to Create the Standby Database (CSD) on the standby server. This option is available in the GUI under the SETUP menu option or under the command line option 7 when you run "dbvisit_setup". In my case I pre-created the /u01/oradata and /u01/flash_recovery_area folders on the standby server (dbvaws01) as root and then made sure it was owned by oracle before I started the Create Standby database process.

Once you have completed the standby database creation process you you can schedule Standby to run as normal either via the Dbvisit GUI (Dbvserver) scheduler or via the Unix cron schedule. Standby can now be used as normal.

I hope this overview gave you a good idea as to how you can get started in using Standby with Amazon AWS. All the best for this as you try this out for yourself, and please feel free to post your own comments and experiences around this. Enjoy!

IT Manager


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