Thursday, 23 February 2017

Getting started with Oracle Database 12c Multitenant Architecture

Oracle database, since its inception, has always used a very specific and unique architecture which served it very well. In earlier forms of this architecture, all components of the database were meant to work in a one-to-one mapping with each other. But from version 12c onwards, a completely new architecture has been introduced – Oracle Multitenant. In other words, from 12c onwards, there are two ways to create a database, as a multitenant database or a pre-12c non-multitenant database. In this series, we will learn how this new architecture works, build components within the new architecture, and learn how to manage different aspects of it, such as backup and security. In this first article, we’ll learn about the necessity of this new architecture and about its core components.

Wednesday, 22 February 2017

Policy-Managed Oracle RAC One Node Databases

Oracle RAC One Node, introduced in Oracle Database 11g Release 2 (11.2.0.2), is a single instance of an Oracle RAC-enabled database running on one node in a cluster. It lets you consolidate multiple databases onto a single cluster while providing high availability benefits of failover protection to the single instance databases.

Oracle RAC One Node databases can be configured to be administrator-managed or policy-managed.

Administrator-managed Oracle RAC One Node Database: The database instance executes on one of the servers from the specified list of candidate nodes. Candidate servers reside in the Generic server pool and as long as at least one server from the candidate list is available, database availability is ensured.

Tuesday, 21 February 2017

Oracle for Absolute Beginners: Date, Timestamp and Interval

All databases stand on a tripod of datatypes: strings, numbers and dates. And though they might dress them in fancy clothing – varchar2, clob, float, integer – strings are really just strings, and numbers are really just numbers. But dates — dates are interesting.

In this article I’ll talk to you about dates, about time, and about how both are captured and calculated in an Oracle database.

The DATE Datatype

DATE is the main – or rather, original – datatype used in Oracle for holding dates. Beneath the plainness of its name, it hides a little depth.  Firstly, for example, it doesn’t really hold a date, instead it records a datetime. It’s a seven byte store of century, year, month, day and hour, minute and second.