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## 9.3 Configuring Lost Update Detection

Prevent form users from overwriting one another by configuring the Lost Update Detection.

Lost updates occur when two or more users try to update the same data, and the last update overwrites updates made by the previous user. To prevent this, updates can check the existing column value(s) in the database with the value(s) retrieved when the record was originally queried.

Configuring Lost Update Detection, you configure the Form region Attribute, Lost Update Type, and enable the Prevent Lost Updates attribute for the corresponding Form - Automatic Row Processing (DML) process.

To enable Lost Update Detection:

1. Create a form region using the Create Page Wizard.
2. View the page containing the form region in Page Designer.
3. In the Rendering tab, select the form region.
4. In the Property Editor, select the Attributes tab.

   The Property Editor displays the attributes. Attributes are organized in groups. To find a group or attribute, enter keywords in the Filter Properties field. The Property Editor displays the group or attributes. Or, you can click Go to Group and select the group.

   Tip:

   To view help for an attribute, select the attribute in the Property Editor and click the Help tab in the central pane.
5. In the Property Editor, find the Edit group and configure the Lost Update Type attribute. Options include:

   - Row Values - A checksum value is calculated for each row, when initially querying the data. The checksum is calculated by concatenating all of the updateable columns into a string and then generating a unique value. When committing the updated record, this checksum is compared to the checksum value.

   - Row Version Column - If your database table includes a column which is incremented every time a record is updated, preferably by a database trigger, then this column can be used instead of calculating checksums. Oracle does not recommend this option if your form updates data in multiple tables.

   Next, update the corresponding Form - Automatic Row Processing (DML) process.
6. In the left pane, click the Processing tab.
7. Find and select the corresponding Form - Automatic Row Processing (DML) process.
8. In the Property Editor, find the Settings.
9. For Prevent Lost Updates, select On.
10. To save your changes click Save. To save and run the page, click Save and Run Page.

See Also:

Editing Pages in Page Designer

Parent topic: Developing Forms