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Don Burleson Blog 







Oracle RAC Deployment Tips

Oracle Database Tips by Donald Burleson


The RAC database provides the technology of cache fusion, which simplifies application deployment issues. Before cache fusion had been fully implemented, many of the applications had to selectively access the multiple instances in a way that would not result in update contentions, thereby minimizing pings and false pings.


With the full implementation of cache fusion, many types of applications are able to connect and use the multiple RAC instances while avoiding the performance issues that result from cross instance updates. There are two broad types of data access methodologies:

  • OLTP:  Traditionally, online transaction processing (OLTP) users access the database resources or data blocks randomly. The transaction life, or access duration, is usually very short. With this method, there is limited conflict or contention with the data sets.

  • DSS:  Decision support systems (DSS) and data warehousing (DW) applications focus more on analysis of the data and the creation of various reports. A data warehouse is a relational database that is designed for analysis rather than transaction processing. A data warehouse usually contains historical data that is derived from transaction data as well as from other sources. The warehouse separates the analysis workload from transaction workloads and consolidates data from several sources.

Using tools such as online analytical processing (OLAP) extraction engines or other statistical tools, large data sets are processed. With this method, for any given query a large number of data blocks are read and analyzed. Performance is a crucial factor with this type of access.


The OLTP and DW databases have traditionally been separated into different servers and instances. The data warehouse is updated or refreshed by loading data from the OLTP on an appropriate schedule. Data warehouses typically use an extract, transport, transform, and load (ETL) process, which involves complex and time-consuming steps such as data exports and network copies. The mixed OLTP and DW databases used to compete often for resources, resulting in update contentions. This created performance issues.


With multiple instances, the RAC database is in a perfect position to segregate the activity on different nodes while still maintaining single database storage. This not only results in better performance levels for both types of data activities, OLTP and DSS, but also gives administrative flexibility and cost savings.

Database Consolidation

The main purpose of database consolidation is to reduce cost.  Today, when so many software choices are supposedly free, DBAs see the number of MySQL and PostgreSQL installations growing.  However, Oracle continues to dominant in the area of Enterprise Applications.  LAMP (Linux, Apache, MySQL, and PHP) development is growing, but many Enterprise level applications, in the authors' experience, do not support MySQL or PostgreSQL.


For 2015, Fortune magazine ranks Oracle Corporation as the sixth (6th) most profitable technology company, making $4.3 billion.  Google came in seventh (7th) place.  MySQL and PostgreSQL have a long climb ahead of them before they are major players in the Enterprise Application market.


As CTOs are forced to cut costs, one trend is to consolidate databases and use Oracle Standard Edition where the features of Oracle Enterprise Edition are not needed.  This could be called license scale-down.  The cost savings of using Standard Edition in place of Enterprise Edition can be significant.  It is important to understand what features and options are only available to Enterprise Edition.

Oracle Grid and Real Application Clusters

See working examples of Oracle Grid and RAC in the book Oracle Grid and Real Application Clusters.

Order directly from Rampant and save 30%. 



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