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Oracle Cloud Infrastructure (OCI) – 1 – Fundamentals

Cloud infrastructure is the most basic products delivered by cloud computing companies through the infrastructure as a service (IaaS) model.  You can create your own IT infrastructure complete with processing, storage and networking resources. Cloud Infrastructure companies provide you flexibility in infrastructure design so these infrastructure setups can be easily set up, replaced or deleted as opposed to a physical one, which requires manual work.

Most Cloud infrastructure will mention below benefits to you:

  • Less capital requirement
  • Less total cost of ownership
  • Flexibility
  • Scalability

There are many Cloud infrastructure companies in the market. Oracle Cloud Infrastructure (OCI) is one of them. OCI use some terms and phrases very frequently  so it is very important first to understand and remember some key terminology.

Some key terms/concepts are :


A hypervisor is also can be called a virtual machine monitor (VMM). It is computer software, firmware or hardware that creates and runs virtual machines. A computer/server on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine.



Physical host machine is known as “bare metal host”.  Example, if you purchase a physical server for your business you can also call it with this fancy name “bare metal host”. Now OCI provides you the control of these physical machine (BARE METAL HOST) without purchasing them.  You do not share these physical machine with any other tenants. The complete physical server (bare metal host) is dedicated to your business.



Bare metal compute instances run directly on bare metal host without any hypervisor. You are the sole owner of the physical CPU, memory, and network interface card (NIC) which bare metal compute instance uses. You can configure and utilize the full physical machine as per your need as if the physical machine is running in your own data center.

Now assume that you want to start your business in New York and your business will be targeting US “region”. you purchased your own server which you plan to keep in your data center. Your goal will be that your server remains in US “region” as your customers are in US.  Since your business is critical and you can’t risk losing your data at any cost so you will buy two servers instead, one you will keep in Chicago and one you will keep in Florida. You will keep data in sync between these two locations so that data remain “Available” to you always. Below are the two terms OCI use for these concepts



A region is simply a localized geographic area where OCI servers are kept. Example Phoenix, AZ is one such region



An availability domain is one or more data centers located within a region. So if Phoenix, AZ is one “region” then in that region there will be different availability domains like PHX-AD-1, PHX-AD-2

Availability domains are isolated from each other and are fault tolerant. So it will be wise for your critical business to use multiple availability domains when you configure your cloud services. This will ensure high availability  and will protect against resource failure.



This is a web-based user interface which you can use to access and manage your services running on Oracle Cloud Infrastructure.



Oracle Cloud Infrastructure (OCI) serves multiple clients worldwide. Every region and availability domains has huge number of servers in place. You as a customer are considered as tenant. Oracle will create a “Tenancy” for your company. Idea is to create an isolated “partition” for your company within Oracle Cloud Infrastructure where you can create, organize, and administer your cloud resources.



Take an example that you rented a building for your business which has many rooms. You labeled each room as per your need say tool room, store room, finance room etc. and you give access to these rooms as per the individual’s need/authority. This is physical way of making sections or compartments. In similar way compartments are made in OCI although those are virtual.

In OCI, a “compartment” is a collection of related resources (such as instances, virtual cloud networks, block volumes) that can be accessed only by certain groups that have been given permission by an administrator. Compartment will act as a filter for what you are allowed to view.

Your “tenancy” is considered your “root compartment” which has all your cloud resources . Inside that root compartment, you will create sub compartments and create policies to give users access on those compartments.



Oracle Cloud Infrastructure (OCI) resources has an Oracle-assigned unique ID called an Oracle Cloud Identifier (OCID). This resource’s ID information can be located in

both the Console and API.



VCN is the secret sauce of cloud providers. It is a customizable private network. VCN provides a single virtual network and a consolidated way to control and secure your enterprise, including all your business units, cloud services, edge/IoT and data center workloads. Please keep in mind that VCN is not a standalone product, but it is a collection of solutions working together.

With the VCN, you as a client gets a private IP space, in which you can create subnets, routing tables and set up firewalls. For isolation of related resources, you can set up multiple VCNs too. So a single tenancy (an Oracle Cloud Infrastructure account) can have multiple VCNs, thereby providing grouping and isolation of related resources.



After you have taken access to the servers/bare metal hosts situated at one of the region of Oracle Cloud Infrastructure the next logical step will be to start utilizing the resources. For that purpose you will create an “instance”, which is a compute host running in the cloud



The above instance that you created will need to run some Operating System (OS). That operating system (and few other software) will be written as a template on a virtual hard drive. This virtual hard drive containing OS and software is known as “image”.  Oracle provides few set of images which you can use. You can also save an image from an instance that you have already configured to use as a template



When you are going to create an “instance” using your own or Oracle’s provided image, then next thing you will decide is how much memory/CPU you want to give to your instance.

These properties are defined by the “shape” which specifies the number of CPUs and amount of memory allocated to the instance. Oracle Cloud Infrastructure offers various different pre-built shapes to fit various computing requirements.



This is used to connect to Oracle Cloud securely. There will be two set of key files – private and public. You upload your public key to Oracle Cloud Infrastructure. You keep the private key securely on your computer so that you can authenticate yourself.

Oracle Cloud Infrastructure uses two types of key pairs for specific purposes:

1) Instance SSH Key pair: This key pair is used to establish secure shell (SSH). DBAs/UNIX Admins are well aware of it.

2) API signing key pair: You use this mechanism when you access Oracle Cloud Infrastructure via the API.  This key pair is in PEM format and is used to authenticate you when submitting API requests.



A block volume in simple word is a hard drive where you stores data. Similar to hard drive, the block volume can also be detached from one instance and attached to another instance without losing data. You will use a lot of block volumes in Oracle Cloud to store your important live applications data.



You will have some data which do no change very frequently like data backup, static files, logs. Such kind of data you can store in object storage. Data will be stored as “object” and each data file can be of 50 GB. Another good thing about object storage is that you can access it from anywhere in VCN.



Objects that we described above will be stored in “bucket”. A bucket is simply a logical container in “OBJECT STORAGE” where you store your data and files.

Above are some of the key terminology. There will be some more useful terms which we will be discussing in coming posts as we explore more on OCI.

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Brijesh Gogia

I’m an experienced Oracle Applications DBA with more than a decade of full-time DBA experience. I have gained a wide knowledge of the Oracle software stack and have worked on several big projects for multi-national companies. I enjoy working with the leading-edge technology and have passion for database performance and stability. Thankfully my work allows me time for researching new technologies (and to write about them).
You can connect with me on LinkedIn.

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