Oracle Database Appliance (ODA)^[1], was introduced by Oracle Corporation in September, 2011. It is a member of Oracle's family of Engineered '''Systems. Engineered Systems are a combination of hardware and software integrated to reduce the cost and complexity of IT infrastructures while increasing productivity and performance. Oracle Database Appliance is a solution that contains the hardware, networking, storage and software needed to build a highly available two-node clustered database server.^[1] The Oracle Database Appliance is a 4U rack-mountable system specifically designed to run Oracle Database Enterprise Edition^[2], with redundant and hot swappable components built-in to meet high availability requirements. Each system has redundant server nodes, interconnects, storage controllers, power supply units and cooling fans. In addition, disk and flash storage are double or triple-mirrored and are shared to ensure redundant data availability and accelerated database performance.

Oracle Database Appliance supports application workloads through Oracle Virtual Machine, (OVM), virtualization. The Oracle Database Appliance, with virtualization, provides efficient sharing of the platform with applications, provides capacity-on-demand licensing for both the database and applications, and allows users to dynamically grow and shrink database and application capacity without restrictions.

Oracle Database Appliance virtualization allows developers to build a Solution-In-a-Box ^[3] that may include an application, middle and database tier using pre-built Virtual Machine templates. There are pre-built Virtual Machine templates for Oracle Enterprise Business Suite, JD Edwards, Business Intelligence, PeopleSoft, Oracle Enterprise Manager, Weblogic Server and others. In-a-Box solutions reduce the total amount of time to deploy complex application environments, especially in remote or branch office locations.

Oracle introduced its first Engineered Database System, Oracle Exadata^[4] in 2008.

In 2011, Oracle announced the next Engineered System, the Oracle Database Appliance^[5], which was an entry level system to introduce customers to the advantages of engineered systems. The Oracle Database Appliance is smaller than the Oracle Exadata, containing less storage, memory and CPUs, at a lower price point. Oracle

Oracle Database Appliance fills the gap in Oracle's product line beneath Oracle Exadata, targeting mid-market customers.

The first version of Oracle Database Appliance, referred to as Version 1 or V1, was first introduced on September 21, 2011. Version 1 was primarily a highly available database server designed to be extremely simple to install, deploy and manage.

The second generation, X3-2, of Oracle Database Appliance was announced in March 5, 2013 and it significantly increased the computing power by using faster processors with more cores, increased memory and larger raw shared storage resulting in greater usable storage. In addition, it offered an optional Virtualized Platform, and embedded the Oracle Virtual Machine(OVM), which allowed the ODA to be much more than a database server only. With OVM, user defined virtual machines can be created for application and middle tier components and allowed users to create a ‘Solution-in-Box’. With the option to create virtual machines, users gained significant configuration flexibility for a variety of solutions.

The current version of the Oracle Database Appliance is now the X4-2, which was announced December 4, 2013 and included faster Intel processors.

A comparison of the Oracle Database Appliance generations:

Servers: The Oracle Database Appliance X4-2 is a 4 Rack Unit, (RU), system that consists of two servers and one storage shelf. Each server contains two 12-core Intel Xeon E5-2697 v2 processors, providing up to 24 enabled-on-demand processor cores and 256 GB of memory per server for a total of 48 processor cores and 512 GB of memory per appliance.

Storage: The Oracle Database Appliance X4-2 base configuration shares twenty 900 GB SAS Hard Disk Drives in a single storage shelf between the two servers, however, the appliance also supports an optional storage expansion shelf. The additional storage shelf doubles the storage capacity of the system for a total of 36 TB of raw storage that may be double-mirrored or triple-mirrored, offering Oracle Database Appliance X4-2 4 18 TB or 12 TB, respectively, of resilient usable database storage. There are four triple-mirrored 200 GB Solid-State Disks, (SSD), per storage shelf for the Oracle Database REDO logs to boost performance and to protect the database in case of instance failure. To expand storage outside of the appliance, external NFS storage is supported for online backups, data staging, or extra database files. The Appliance Manager in conjunction with Oracle Automatic Storage Management (ASM) automatically configures, manages, and monitors disk performance and availability. The Appliance Manager also provides alerts on performance and availability events as well as automatically configuring replacement drives in case of a hard disk failure.

Networking: The two server nodes are connected via a redundant 10GbE interconnect for cluster communication. Each server also provides the option for 10GbE SFP+ (fiber) or 10GBase-T (copper) external networking connectivity, ensuring the appliance will be compatible with any data center.
  

The Oracle Database Appliance X4-2 supports the following database and operating system software:   

Oracle provides a deployment tool called the Appliance Manager to simplify the deployment and make it less time consuming. Oracle provides special patch bundles for the Database Appliance, consisting of firmware, Linux OS, clustering, storage management, and database patches, which have been tested for compatibility^[5] and greatly simplifies systems administration activities.^[7]

Customers may choose to license only a subset of the processor cores in the Oracle Database Appliance. This ‘Capacity-on-Demand’ license model allows users to define configurations with just the number of processor cores needed for their workloads and is implemented by disabling unnecessary processor cores in the BIOS, using a special interface. Cores can be enabled at a later time, allowing customers to increase the capacity of the appliance if required,^[6] and reducing the initial total cost of implementation. 

In bare metal configurations, cores are enabled in increments of 4 cores on each node and with virtualized configurations cores can be enabled in increments of just 2 cores on each node.

The Oracle Database Appliance is a fixed configuration as described above. Customers cannot cluster multiple appliances together to create a larger cluster (beyond 2 servers).