About Oracle Database ReplicationStreams, Data Guard and RACReplication is the process of using a set of supplied database management PL/SQL packages and procedures coupled with a supplied toolset of network utilities to enable the sharing of database objects and data between multiple databases. To maintain replicated database objects and data between multiple databases, a change to one of these database objects in a database is shared with the other linked databases. In this way, the database objects and data are kept synchronized within all of the databases in the replication environment. Oracle Streams ReplicationIn a Streams replication environment, the database where a change originates is called the source database and a database where a change is shared is called a destination database. There can be more than one source and more than one destination database. Ready for production use in Oracle 10g, Oracle Streams allows near real-time replication and support for master-to-master replication. Oracle Streams has no licensing costs and it is less complex to configure than a RAC database. Non-identical Replicas with StreamsStreams replication supports sharing database objects that are not identical at multiple databases. Different databases in the Streams environment can contain shared database objects with different structures. You can configure rule-based transformations during capture, propagation or apply to make any necessary changes to LCRs so that they can be applied at a destination database. Sub-setting with StreamsStreams also supports sub-setting of table data through the use of subset rules. If a shared table in a database in a Streams replication environment contains only a subset of data, then you can configure Streams to manage changes to a table so that only the appropriate subset of data is shared with the subset table. For example, a particular database can maintain data for employees in a specific department only. In this case, you can use subset rules to share changes to the data for employees in that department with the subset table, but not changes to employees in other departments. What is DataGuard?Created as a disaster recovery solution, DataGuard is also a solution for high availability. It can be used to replicate and maintain production databases which can be used to alleviate reporting job traffic on the server. DataGuard has the requisite knowledge of the Oracle database to reliably protect the standby database from corruptions that attempt to propagate from the primary database. It is straightforward to implement and manage. It also enables all standby databases, both physical and logical, to be used for production purposes while in standby role (testing, backup, upgrade). DataGuard delivers:
DataGuard can be configured for real-time consistency between the production database and from one to as many as nine standby databases or, delayed by a set time to allow the standby to become a snapshot standby. DataGuard becomes especially useful for testing and rolling upgrades and can be configured as either a physical (Redo-Apply) or logical (SQL-Apply). Each has its advantages and inherent flexibility. Oracle Real Application Clusters—An Active/Active ClusterOracle Real Application Clusters (RAC) is an option of Oracle Databases. Oracle RAC is a cluster database with a shared cache architecture that overcomes the limitations of traditional shared-nothing and shared-disk approaches to provide highly scalable and available database solutions for all business applications. Oracle RAC is a key component of Oracle enterprise grid architecture. Most users of Oracle RAC employ a two node cluster to insure always available service to its user community. The two node configuration offers the flexibility needed to perform maintenance, upgrades and patching without interfering with user activity. Other organizations needing higher throughput employ multiple nodes of 6, 12 and even 32 all running on separate servers but servicing the same database. These organizations are usually servicing very large databases for a very large user community. Companies using a clustered database generally want to load balance their workload across the cluster. Starting with Oracle RAC 10g Release 2, the load balancing advisory provides real-time information to the application tier at the service level being provided by the database. Applications can utilize this information to provide the best possible throughput or transaction response time to the application using the assigned resources in the cluster. Oracle RAC includes a highly available (HA) application framework that provides the necessary service and integration points between RAC and custom enterprise applications. One of the main features of a highly available application is the ability to receive fast notification when something happens to critical system components (both inside and outside the cluster). This allows the application to execute event-handling programs. The timely execution of such programs minimizes the impact of cluster component failures by avoiding costly connection timeouts, application timeouts and reacting to cluster resource reorganizations, in both planned and unplanned scenarios. The current version of Oracle RAC comes with its own network clustering interface allowing easier installation and configuration on Windows, UNIX, and Linux-based systems. A recent development in the use of RAC with virtual machines is greatly reducing operating costs for IT departments. Why You Should Consider Replication
While DataGuard provides an invaluable fail-over option, RAC is now the premier clustering architecture for an unbreakable, always available database. Its unique active/active architecture insures that data is always available and performance is optimal. When set up with the transparent application fail-over option, a database server can experience scheduled or unscheduled downtime without interruption of service. What You Can Expect From XtiviaXtivia’s certified Oracle engineers will provide recommendations on replication methods and implementation strategies to set up a database replication configuration of your choice to that will meet your organization’s needs and objectives. Xtivia engineers will install, configure and document a replication system or assist your staff with complex project tasks. Xtivia also provides the Virtual-DBA system to monitor your replication server activities and status. Xtivia delivers:
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