Thursday, March 17, 2011

Oracle Database on Amazon RDS

Recently, Amazon and Oracle announced that they are going to make "Oracle 11g Database" available on Amazon AWS as a service. It's being brought into AWS's RDS feature which currently offers "MySQL database as a service".

Amazon RDS is a web service that allows you to set up, operate, and scale a relational database in the cloud. You can provision a relational database (currently only MySQL) on RDS in just a few minutes. Amazon RDS will also manage database administration tasks including continuous backups, software patching etc.
When launched (sometime in Q2 of 2011), you will have the option to choose from the licensing options for running the Oracle Database on Amazon RDS ->
  • Bring Your Own License – (BYOL): Customers with existing Oracle Database licenses can run Oracle Databases on Amazon RDS with no additional software licensing or support cost. Oracle will provide the technical support required in case BYOL DB instances. 
  • On-Demand Database Instances: This is a pay-by-the-hour licensing option with no up-front licensing fee or long-term commitment required. One simply pays by usage depending on the database edition and size of the instance. Brings it on par with other AWS offerings. Technical support for On-demand instances will be provided by AWS.
  • Reserved DB Instances: Make a commitment and pay a one-time fee to get a DB instance with a significant discount on the hourly usage charges. The commitment required would be 1 or 3 years. Technical support for On-demand instances will be provided by AWS.
 While you can still choose to install Oracle on an AWS EC2 instance but it had a few drawbacks –>
  • Licensing fee – Oracle is an expensive product and it acted as a deterrent to use Oracle on a cloud hosting platform such as Amazon.
  • High availability – currently setting up of Oracle RAC is not possible on AWS EC2 hence one cannot achieve high-availability
Given the above mentioned points it definitely was not possible for startups, SMB segments to consider Oracle as the database of their choice. So I believe making Oracle available on RDS is a very good move. However a few things to watch out for –
  • Upgrades – Can I choose to opt out of any future upgrades because I don’t want to be forced for an upgrade. E.g. they have similar option available for MySQL so will it be extended to Oracle as well?
  • High availability – Would I get RAC? Will it be made available on-demand or forced choice? 
  • Data security – Database on shared infrastructure adds the same security concern that’s being on people’s mind for quite some time. Admin controls being with Amazon could be another concern.
  • Manageability – How much control do I get and the need to learn a new API to manage the databases.
  • TCO – Don’t just go by the hourly usage charges as Amazon will also charge for storage (backup and data), bandwidth / data transfer etc.
It would be good to hear about others opinion and experience.

Tuesday, March 8, 2011

Edition based redefinition

Oracle 11g brought in a new feature called Edition based redefinition (EBS) basically aimed at reducing the planned downtime during application releases/upgrades etc. In this changing and dynamic world, application also undergoes numerous enhancements; it’s in these situations that one cannot afford to take a downtime and looks for options to minimize or eliminate them. While the application code and the software provide some options, the Oracle database engine had no such option.  

Till recently, Oracle database had only few options – such as online index rebuild and table redefinition to address planned downtime [Also has Workspace manager; Thanks for pointing out Gary Myers]. However, we all know Oracle’s capability to address unplanned downtimes with features such as – Real Applications Cluster (RAC), Physical / logical standby database, Streams etc.

With 11gR2, Oracle claims to have addressed the gap with edition based redefinition.  Oracle now supports multiple versions (editions) of a given object. So now, the objects are called as “editioned object” or “non-editioned objects” based on whether an object can have multiple versions or not. While one version of the object is used by the live application, the other version can be used to carry out changes and tested before making it permanent. However, the editionable feature is available for the following database objects ->
  • Synonym
  • View
  • Procedure
  • Function
  • Package and Package Body pe
  • Trigger
  • Type and Type Body
  • Library
The all-important and most used object – table and indexes are missing from the above list. So if you look at the list, you will feel that the versioning of code is now extended to database engine. Only view (though that’s also a piece of SQL code) and synonyms have been added. However, one can work around table by creating views and making them editionable but again only simple views without the use of functions etc. can be editioned. As a change, the developer needs to make his/her code work against editionable objects.

The other important thing is data within the table can’t be versioned; a lot of changes happen to be DML in nature so this is another important thing missing though there are workaround.

So, in my opinion this feature is useful in the following scenario =>
  • If you make changes to procedures, function etc.
  • Changes are done to physical structure of tables rather than data
Otherwise I feel this is not as useful yet. Also it’s a relatively a new feature and yet to mature. I'm sure future releases of Oracle will bring in some enhancements.
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