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Application Deployment Issues

Oracle RAC Cluster Tips by Burleson Consulting

This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters.  To get immediate access to the code depot of working RAC scripts, buy it directly from the publisher and save more than 30%.


There are many applications that are designed in such a way that the user connections or application instances act on different sets of data blocks. This kind of situation provides good scalability. There is minimum contention for the data blocks. At the same time, many of the applications need 24/7 support.

The following section will show how each of the categories that use the RAC database uses the architectural advantage.

OLTP Applications Using Exclusive or Specific Data

In this type of application, the RAC system gives almost linear scalability. Instead of using a stand-alone database with limited resources, the RAC database provides more than one database instance, allowing applications to connect to any of the instances. For example, a bank branch is accessing the central database system. Any particular branch usually inserts or updates only the data pertaining to it. It rarely needs to access another branch?s data. This kind of arrangement allows a set of branches to be grouped by region or load, say, on instance one. Another group of branches accesses instance two, and so on. Since the data blocks of one branch are rarely spread across multiple instances, scalability is almost linear, with nearly zero cross instance transfers.

Departmental Applications

Extending the analogy explained above, assume that there are many functional entities or departments accessing a common RAC database system. For example, human resources, sales, distribution, manufacturing, and finance all access the same database system. Each of these functional units has a set of data. It is very rare that the data pertaining to one department is needed for another department.

In this case, access can easily be vertically partitioned. For example, sales and distribution can access through instance one, human resources and finance can access through instance two, and manufacturing can access through instance three. All these applications modify different sets of tables. Conflicts and cross instance block transfers are minimized.

Data Warehousing Applications

DW applications involve large and complex queries against a huge database. Data warehouses are designed to accommodate ad hoc queries. It might not be possible to anticipate the workload of a data warehouse in advance, so a data warehouse should be optimized to perform well for a wide variety of possible query operations.

DW is updated on a regular basis by the ETL process, which is run nightly or weekly, using bulk data modification techniques. ETL stands for extraction, transformation, and loading. The end users of a data warehouse do not directly update the data warehouse. During the data loading, SQL queries accessing the data may experience poor response times owing to low memory resources.

Compared to a typical OLTP operation, which accesses only a handful of records, a typical data warehouse query scans thousands or millions of rows or data blocks. For example, a DW query may be asking to find the total sales for all customers last month or analyze the stock price of the airline industry during the current year.

To meet these kinds of challenges, parallel processing is an apt solution. Oracle?s parallel execution feature uses multiple processes to execute SQL statements on one or more CPUs. Parallel execution is available on both single instance and Real Application Clusters databases.

Real Application Clusters takes full advantage of parallel execution by distributing parallel processing to all the nodes in the cluster. The number of processes that can participate in parallel operations depends on the degree of parallelism (DOP) assigned to each table or index.

Since the RAC solution provides multiple instances, the instance that uses SQL queries can effectively be separated from the instance that is specialized for data loading and ETL processing.

Applications Requiring HA

Many mission critical applications, like brokerage trading systems, airline traffic movement, credit card sales, online shopping, and retail banking, etc., cannot afford to have any downtime. All these applications are heavily dependent on the database systems.

The RAC database provides an ideal solution to withstand node or host failures. With multiple nodes, redundancy is built into the database system.

 


This is an excerpt from the bestselling book Oracle Grid & Real Application Clusters, Rampant TechPress, by Mike Ault and Madhu Tumma.

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.

http://www.rampant-books.com/book_2004_1_10g_grid.htm


 

 
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