Operating Systems: i5/OS
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Set the run time for CMP sequence groups
By designating CMP sequence groups for entity beans, you can prevent
certain types of database-related exceptions from occurring during the run
time of your EJB application. Within each group you specify the order in which
the beans update your relational database tables.
When you define a sequence group, you designate it as one of two
types:
- RI_INSERT, for setting a bean persistence sequence to prevent database referential integrity (RI) violations
- UPDATE_LOCK, for setting a bean persistence sequence to minimize exceptions
resulting from optimistic concurrency control
Overview
Both types of sequence groups must be created after you have assembled
the beans into an EJB module, prior to installing your application on the
product. If you need to edit sequence groups, uninstall the application,
make your changes using the following steps as a guide, and then reinstall
your application.
Note: If you already selected or plan to use top-down mapping
for mapping your enterprise beans to back end data, you do not
need to create a sequence group with an RI_INSERT type. The product does not
generate an RI policy for the database schema that it creates when you select
top-down mapping.
Procedure
- Start an assembly tool. Refer to Starting WebSphere Application
Server Toolkit in the Application Server Toolkit documentation.
- Open the J2EE perspective. Click Window > Open perspective >
J2EE.
- In a J2EE hierarchy view (Window > Show view > J2EE hierarchy),
right-click the EJB module containing beans that require sequence grouping,
and click Open with > EJB deployment descriptor editor. The
EJB deployment descriptor editor for the module is displayed in a view.
- Click the Overview tab.
- In the EJB CMP sequence groups section, click Add.
The EJB CMP Sequence Group wizard panel is displayed.
- Type a name for your sequence group.
- Type your group type designation in all capital letters: RI_INSERT
or UPDATE_LOCK
- In the Available Beans list, highlight the first bean that
you want to place in the group. Click the arrow pointing toward the Selected
beans list. The bean name is removed from the Available
beans list and is displayed in the Selected beans list.
- Repeat the previous step until you complete your sequence group.
You must add each bean in the order that you want the persistence manager
to handle it. In the case of delete operations for an RI_INSERT group, the
persistence manager reverses the order that you designate and deletes the
beans and their corresponding database rows accordingly. If you need to alter
the sequence of your group, select a bean and click the arrow to move the
bean one position vertically.
- Save your changes to the deployment descriptor.
- Close the EJB deployment descriptor editor.
- When prompted, click Yes to indicate that you want to
save changes to the deployment descriptor.
You also can save changes to deployment descriptors at any time by pressing
Ctrl+S.
What to do next
You are now ready to deploy your
EJB module or combine
it with other modules into a J2EE application.
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Sequence grouping for container-managed persistence
Related tasks
Deploying and administering J2EE applications
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