Adding a column for collision detection when generating a top-down mapping

This task describes how to add a column for collision detection when generating a top-down mapping.

Before you begin

Prerequisite tasks

Create a version 1.3 or 1.4 enterprise application project with a target server of WebSphere® Application Server v6.x.
Create a version 2.x EJB project in the enterprise application project you created.
Create or import a 2.x CMP beans in the EJB project that correspond to the enterprise application project you created.
Set up the optimistic access intent to wsOptimisticUpdate or wsOptimisticRead.

Steps for this task

To generate a collision detection column for top-down EJB 2.x CMP entity bean, complete the following:

Refer to the generating a top-down mapping task.
In the EJB to RDB Mapping wizard, select the optional check box Add a column for collision detection.

Post task

Before using the collision detection column, you must complete the following:

Create your own database trigger to support the use of the collision detection column.

Results

Adding a column for collision detection results in the following events:

The collision detection column is displayed in the Tables pane of the Mapping editor.
The default data type of the collision detection column is BIG INTEGER.
The naming convention of the collision detection column has the following format: OCC_beanName
The top-down mapping generates an extra relational column. By default this column is not mapped as illustrated there is no mapping arrow icon.
If you choose to use collision detection column, the use of the collision detection column takes precedence over the alternative optimistic concurrency control scheme of including attributes in a predicate for optimistic access intents. In addition, all the optimistic predicate settings are ignored for optimistic access intent.