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Considerations for Receiving Database Change Notifications Using the Oracle Database adapter

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This topic provides some considerations and best practices that you must keep in mind while using the Oracle Database adapter to receive database notifications from an Oracle database.

Considerations While Using the Adapter to Receive Notifications

You must consider the following while using the Oracle Database adapter to receive query notifications.

  • The Oracle Database adapter simply passes on the notification, which it receives from the Oracle database, to the adapter clients. The adapter does not distinguish between the notifications for different operations, i.e., the adapter does not have any information whether a particular notification is for an Insert operation or an Update operation.

  • The notification message for an operation is not affected by the number of records affected by that operation. For example, irrespective of the number of records inserted in an Oracle database table, the adapter clients receive only one notification message.

  • We recommend that the adapter client application contain the logic to interpret the kind of notification received from the Oracle database. The adapter client applications can do so by extracting the information in the <Info> element of the received notification message. Here’s an example of a notification message received for an Insert operation.

    <?xml version="1.0" encoding="utf-8" ?>   
<Notification xmlns="http://Microsoft.LobServices.OracleDB/2007/03/Notification/">  
  <Details>  
    <NotificationDetails>  
      <ResourceName>SCOTT.ACCOUNTACTIVITY</ResourceName>   
      <Info>1</Info>   
      <QueryId>0</QueryId>   
    </NotificationDetails>  
  </Details>  
  <Info>Insert</Info>   
  <ResourceNames>  
    <string xmlns="http://schemas.microsoft.com/2003/10/Serialization/Arrays">SCOTT.ACCOUNTACTIVITY</string>   
  </ResourceNames>  
  <Source>Data</Source>   
  <Type>Change</Type>   
</Notification>

    Notice the value within the <Info> element. This value provides information on the operation for which the notification message was received. Your application should have the functionality to extract the value within the <Info> element and then based on the value, perform subsequent tasks. The topic Processing Notification Messages to complete Specific Tasks in Oracle Database has instructions on how to extract the value within the <Info> element.

  • Ideally, after the client application receives a notification, it should update the record for which the notification is already received so that the subsequent notifications are not for the same record. For example, consider an ACCOUNTACTIVITY table that has a Processed column. For all new records inserted into the ACCOUNTACTIVITY table, the value in the Processed column is always ‘n’. For example, after an insert operation, the records in the ACCOUNTACTIVITY table will look like the following:

    Account Transaction ID Processed
    10001 n

    To get notifications for the newly inserted record, the adapter client will set the NotificationStatement binding property as:

    SELECT * FROM SCOTT.ACCOUNTACTIVITY WHERE PROCESSED = ‘n’

    After, receiving the notification, the client application must set the value of the Processed column to ‘y’ so that the notification statement does not operate on the record that was already notified for. So, to achieve this, the client application must perform an Update operation on the ACCOUNTACTIVITY table. After the Update operation, the same record in the ACCOUNTACTIVITY table will look like the following:

    Account Transaction ID Processed
    10001 y

    Interestingly, the Update operation will again send a notification to the adapter client and the whole process will be repeated again. So, the client application must have the required logic to discard such unwanted notifications.

  • If the NotifyOnListenerStart binding property is true, the adapter will send a notification to the adapter client every time the receive location starts. For more information on how to use the binding property and interpret the notification message, see Receiving Oracle Database Change Notifications After a Receive Location Breakdown.

Typical Orchestration for Receiving Notifications

This section outlines the typical orchestration flow for receiving notifications using the Oracle Database adapter.

  1. The first thing that the orchestration must do is to check the kind of notification received. The things to check for are:

    • Whether the notification was received for the receive location restart.

    • Whether the notification was received for an operation on a database table, such as Insert, Update, or Delete.

      The orchestration must include an Expression shape, and within that an xpath query, to decide what kind of message is received.

  2. After the notification type is available, the orchestration must include a decision block to perform specific actions based on the type of notification received. To achieve this, the orchestration must include a Decide shape. The Decide shape consists of a Rule block and an Else block. Within the Rule block, you must specify the condition and then include orchestration shapes to perform certain operations if the condition is met. Within the Else block, you must include orchestration shapes to perform certain operations if the condition is not met.

    The preceding recommendations are described in detail in Processing Notification Messages to complete Specific Tasks in Oracle Database using BizTalk Server.

See Also

Receiving Oracle Database Change Notifications Using BizTalk Server