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Introduction to Application Deployment for Real Application Clusters

This chapter describes Oracle Real Application Clusters application deployment by explaining considerations for taking advantage of the scalability and high-performance features of Real Application Clusters. This chapter includes the following topics:

• Taking Full Advantage of Oracle9i Features
• Implementing Oracle9i Features with Real Application Clusters

Taking Full Advantage of Oracle9i Features

To optimally deploy applications with Oracle9i Real Application Clusters, consider the issues for the Oracle features described in this chapter. Proper implementation of these features minimizes deployment problems. It also ensures that your system takes full advantage of the breakthrough technology of Cache Fusion and the high-performance features of Real Application Clusters.

The feature descriptions in this chapter provide a starting point for Real Application Clusters application deployment that you can use after implementing single-instance deployment methods.

Implementing Oracle9i Features with Real Application Clusters

The considerations described in this section relate to features that are unique to Oracle and that enhance the performance of Real Application Clusters. The features discussed in this section are:

• Storage in Real Application Clusters
• High Availability and Failover in Real Application Clusters
• The Shared Server in Real Application Clusters
• Connection Load Balancing
• Transparent Application Failover in Real Application Clusters
• PL/SQL in Real Application Clusters
• Recovery Manager (RMAN) in Real Application Clusters

Storage in Real Application Clusters

The advanced storage features of Oracle9i provide exceptional performance for Real Application Clusters. These features include automatic segment-space management, automatic undo management, and the server parameter file. In addition, instead of using raw devices, on certain platforms you can store files for Real Application Clusters in cluster file system files.

Cluster File Systems in Real Application Clusters

Cluster file systems simplify Real Application Clusters installation and administration. Using cluster file systems eliminates the need to manage raw devices. Cluster file systems also offer scalable, low latency, highly resilient storage that significantly reduces costs. Refer to your vendor documentation for details about implementing cluster file systems.

High Availability and Failover in Real Application Clusters

High availability configurations have redundant hardware and software that maintain operations despite failures and that avoid single points-of-failure. When failures occur, failover moves the processing performed by the failed component to a backup component. Oracle's failover process quickly re-masters resources, recovers partial or failed transactions, and rapidly restores the system.

You can combine many Oracle products and features to create highly reliable computing environments. Doing this requires capacity and redundancy planning. In addition, consider your overall system costs and your return on investment. There are also other practical considerations such as selecting the appropriate hardware and deciding whether to use idle machines that are part of your high availability configuration.

Primary/Secondary Instance and Active/Active Instance Configurations

Primary/Secondary Instance configurations are the least complicated type of high availability configuration to configure. These are also the easiest type of configurations to administer. For example, the administrative overhead for a primary database in this configuration is the same as the overhead of a single-instance configuration.

In Primary/Secondary configurations, the second instance does not have to remain idle. For example, you can use the second instance for read-only operations. You do not have exceptional scalability with Primary/Secondary configurations, but you do have high availability.

Active/active instance configurations, on the other hand, have typically been more complex to configure. However, with the advent of Real Application Clusters Guard II, easy to manage full active configurations are available.

Real Application Clusters Guard II

Real Application Clusters Guard II extends the notion of a two-node active/active cluster to an n-node, fully active cluster where all instances can support the services in the cluster database.

Oracle Real Application Clusters Guard I

Oracle Real Application Clusters Guard I, which is an enhanced configuration of Real Application Clusters tightly integrates Oracle's enhanced recovery features within the cluster database framework of your platform.

Data Guard

Oracle9i Data Guard works with standby databases to protect your data against errors, failures, and corruptions that might otherwise destroy your database. Data Guard protects critical data by automating the creation, management, and monitoring aspects of standby database environments. Data Guard automates the otherwise manual process of maintaining a transactionally consistent copy of an Oracle database to recover from the loss or damage of the production database.

The Shared Server in Real Application Clusters

Real Application Clusters with the functionality of the shared server feature can process thousands of concurrently connected database users. Shared server efficiently manages the connection load for many users and it operates similarly to the way that a transaction monitor operates.

Real Application Clusters with shared server significantly enhances the performance of applications running on two or more smaller computers. You do not need to rewrite your applications to use shared server. In fact, some applications perform better with shared server than without.

With shared server configurations, user processes connect to a dispatcher. The dispatcher then directs multiple incoming network session requests to a common queue. When a server process becomes available, the dispatcher connects the incoming request to the idle dispatcher. When the connection is no longer needed, the server process is available for another request. Thus, a small set of server processes can serve a large number of clients.

Connection Load Balancing

The connection load balancing feature automatically distributes connections among active instances. Connection load balancing does this based on the workload of each node and instance in a cluster. You can use connection load balancing, in both shared server and dedicated server environments. Real Application Clusters and Cache Fusion combined with connection load balancing allow you to run all types of applications without application or data partitioning.

Transparent Application Failover in Real Application Clusters

The transparent application failover (TAF) feature automatically reconnects applications to the database if the connection fails. Because the reconnection happens automatically within the OCI library, you do not need to change the client application to use TAF.

Because most TAF functionality is implemented in client-side network libraries (OCI), the client must use the Oracle Net OCI libraries to take advantage of TAF functionality. Therefore, to implement TAF in Real Application Clusters, make sure you use JDBC OCI instead of PL/SQL packages.

You can also use TAF in Primary/Secondary Instance configurations. If you do this, then use the INSTANCE_ROLE parameter in the Connect Data portion of the connect descriptor to configure explicit secondary instance connections.

To use TAF, you must have a license for the Oracle9i Enterprise Edition. Because TAF was designed for Real Application Clusters, it is much easier to configure TAF for that environment. However, TAF is not restricted for use with Real Application Clusters environments. You can also use TAF for single instance Oracle. In addition, you can use TAF for the following system types:

• Oracle Real Application Clusters Guard
• Replicated Systems
• Data Guard

  See Also: Oracle9i Real Application Clusters Concepts for more conceptual information aboutTAF in Real Application Clusters Oracle9i Net Services Administrator's Guide and the Oracle Call Interface Programmer's Guide for more information about TAF Oracle9i Replication for more information about Oracle replication

PL/SQL in Real Application Clusters

PL/SQL is Oracle's procedural extension of SQL. PL/SQL is an advanced fourth-generation programming language that offers features such as data encapsulation, overloading, collection types, exception handling, and information hiding. PL/SQL also offers seamless SQL access, tight integration with the Oracle server, as well as tools, portability, and security.

Recovery Manager (RMAN) in Real Application Clusters

Recovery Manager (RMAN) is an Oracle tool that you can use to backup, copy, restore, and recover each datafile, control file, and archived redo log. You can invoke RMAN as a command line utility or use it through Oracle Enterprise Manager.

RMAN automates many backup and recovery tasks. For example, RMAN automatically locates the appropriate backups for each datafile and copies them to the correct destinations. This eliminates the manual, error-prone effort of using operating system commands to accomplish the same task.

You must configure RMAN so that all instances can access all the archive logs throughout the cluster. When one instance fails, the surviving instance that performs recovery must access the archive logs of the failed instance.

The next chapter examines application development for online e-commerce and decision support systems. The remainder of this book examines the deployment and performance of applications that use Real Application Clusters databases.