Enterprises are investing heavily in their information technology infrastructure because they realize huge benefits in terms of lower business costs, better information and better communications.  They have developed a variety of autonomous and distributed applications to automate business process, and manage business tasks. However, these applications need to communicate with each other, coordinating business processes and tasks in a consistent, reliable, secure, and autonomous manner.  They also need to efficiently exchange information with customers, partners, and suppliers over low-cost channels such as the internet, while preserving a traceable history of events--a requirement previously satisfied through now obsolete paper forms.

Advanced Queuing (AQ) is the message queuing functionality of the Oracle database that satisfies the above needs. Traditional message-oriented middleware address only a sub-set of these needs. AQ's integration with the database brings unprecedented levels of functionality, operational simplicity, security, reliability, availability, and scalability to the world of message queuing. In addition, AQ supports multiple communication channels, including the Internet, to cater to the needs of e-businesses.

Below are some highlights of Oracle Advanced Queuing:

Asynchronous application integration
AQ enables applications to communicate asynchronously. It offers multiple ways for applications to produce (enqueue) message and consume(dequeue) messages. Producer application can enqueue a message for post consumption. With this feature, messages will be visible to the consumer application after the specified delay. Message can be created with an expiration time. If the message is not consumed before its expiry the message is moved to the exception queue. On the consuming end, consumer application has various mechanisms to consume the message. They can process as the messages as they arrive. For that purpose, they can use wait for the messages to arrive. Alternatively, it can be notified when the messages arrive. These notifications can be an OCI callback function, a PL/SQL functions, or even an email. AQ also offers FIFO and priority based ordering of messages.

Extensible Integration Architecture
AQ offers an extensible architecture for integrating distributed applications. It offers multiple models of communication - point-to-multipoint and publish/subscribe. In the point-to-multipoint model, the producer application specifies the recipient list for the message. The publish/subscribe paradigm offers an extensible way to integrate additional applications in the future. Publisher and subscriber applications communicate via queues and need not know about each other. AQ also offers unique content-based subscriptions. Subscriber application can specify interest based on message content.

AQ offers extensible way to handle exceptions. The erroneous message is automatically moved to an exception queue. These exceptions can be handled separately. Exceptions can occur when the message is expired or message can not be successfully dequeued.

Heterogeneous  Data Integration
One of the limitations of most of the messaging systems is the limited type system. With AQ, messaging applications can use the extensive type support offered by the Oracle database. This includes support for Oracle object types and the XMLType supported in Oracle9i. The data model used for messaging operations can be the same as that of the application to be integrated. 

In Oracle9i, applications with different data models can be integrated using the transformation feature. With this feature, customers can define transformation mappings from one data model to another. Later, they can use this mapping, while performing various AQ operations. 

Application Location Transparency
The integrated applications need not be co-located. They may run on different Oracle databases. Messages can be automatically propagated between queues which may be on the same or different Oracle databases. The destination queue is yet another subscriber to the source queue. AQ propagation does not use distributed two-phase commit. Hence, it does not have the in-doubt transactions in case of failures and is also network efficient. AQ offers guaranteed and fail-safe propagation. Propagation is also tunable according to application needs. In Oracle9i, propagation can done over the Internet.

In Oracle9i, AQ is also integrated with Oracle Internet Directory (OID). Queue and event meta-data can now be stored and looked up from  LDAP (OID). 

Unique Message Management Benefits
Providing message queuing from the database offers unique benefits. It brings transactional behavior with very high reliability to the messaging operations. In case of failures, messaging operations are recovered in the same manner as other database operations. With AQ, messaging and database operations can be performed in the same transaction. They can use the same security model for messaging and database operations. This is a unique benefit that tremendously reduces application complexity. Application developers do not need bother about different resources for transactions management, different security schemes, and different data models. 

In many situations, for example, when sending financial information, the messaging operations require not only guaranteed delivery but also reliable auditing. With AQ, messaging operations are automatically audited. An entire message history can be queried using a SQL view. This history can also be used for extracting tracking information and business intelligence.

Unique Features for E-Business
Businesses interact with their customers and partners over the Internet. In Oracle9i, AQ operations - enqueue, dequeue, notifications, propagation - can be performed over the Internet. Now, a very simple and highly performance web application can directly place an order securely over the Internet. This new Internet propagation feature enables integration of applications of business partners over the Internet. An email notification feature sends an email notifications for high-priority activities. A new transformation feature can be used for verification and transformation of incoming and outgoing business messages. 

E-business integration is incomplete without the integration of legacy applications. To integrate with IBM mainframe applications, messages can be automatically propagated to and from AQ to MQ Series. Similarly for integrating with Tibco-based messaging applications, messages can be automatically propagated to and from AQ and Tibco Rendezvous. Please check with Oracle for availability of messaging gateway.

Management with Oracle Enterprise Manager
Oracle Enterprise Manager (OEM) can manage AQ. AQ administrative functionality has been provided through the OEM console. The OEM console can be used to create queuetables, create queues, browse through AQ messages, archive or purge AQ messages, add AQ subscribers, and manage propagation. The OEM console also shows the topology for the propagation of messages between queues at the database and queue level.

The OEM Diagnostics and tuning pack supports alerts and monitoring for AQ queues. Alerts can be sent when the number of messages for a particular subscriber exceeds a threshold. Alerts can be sent when there is an error in propagation. In addition, queues can be monitored for a number of messages in ready state or a number of messages per subscriber, etc.

Closing Statement
Advanced queuing is the full-featured message queuing functionality of the Oracle database.  The unique management functionality offered by AQ can not be accomplished by merely combining a message-oriented middleware and a database. It has unique functionality such as internet access tremendously simplifies e-business interactions.

KEY FEATURES
Asynchronous Application Integration Multiple ways of Enqueue/Dequeue Blocking/Non-blocking dequeue Asynchronous notifications OCI, PL/SQL, Java, Email Ordering and priority FIFO and priority-based ordering Time-based specification for consumption Message delay and expiration	Heterogeneous Data Integration Extensive type support for message structure Oracle object and scalar type support Large objects such as CLOB and BLOB Dynamic message structure with XML Transformation plug-ins Definition in PL/SQL Usage during AQ operations
Extensible Integration Architecture Automatic exception handling Multiple modes of addressing Point-to-multipoint Publish/subscribe Multi-consumer queues dynamic addition of durable subscribers Subscriptions Subject-based and content-based	Application Location Transparency Automatic message propagation Guaranteed, fail-safe Tunable Transport independent Http(s) and email support OID Integration Global queues and events definitions
Unique Message Management Benefits Integrated transaction, security, and programming  model Single model database and message queuing operations Automatic retention Automatic auditing for   tracking, and business intelligence Querying and SQL access SQL access to message and its history	Unique Features for E-Business Internet access to Advanced Queuing Perform AQ operations - enqueue, dequeue, propagation, and notifications over the Internet Transformation plug-ins Use transformation mappings during internet operations Messaging gateway* to MQ Series and Tibco Rendezvous (check with Oracle for availability)
RELATED PRODUCTS AND SERVICES Oracle offers the following tools to make e-business integration easier.  Oracle Enterprise Manager ("OEM"): Administrative tool to manage Oracle database. Oracle Workflow: Tool to model business events and processes. Oracle Application Interconnect:Tool for integrating packaged applications Oracle JDeveloper: Complete enterprise level Java development tool.	GETTING STARTED Advanced queuing is a feature of the Oracle database.  Start using the feature, if you already have Oracle9i Enterprise Edition You can download Oracle9i Enterprise Edition from OTN. You can purchase Oracle9i Enterprise Edition from Oracle store.

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