Understanding APEX concurrency management

APEX provides default mechanism to prevent concurrency or ?lost update? issues within an application.  This mechanism is called ?Automatic Row (DML) Processing?.    The mechanism can automatically be created during the ?Create Page? Wizard or can be added manually afterward.   This approach also provides 2 other advantages: do not have to provide SQL coding for DML actions and APEX will perform the DML actions automatically.  

The ?Automatic Row Processing? mechanism can be added to a form simply by using the ?Create Page? wizard.   When creating a page using one of the Form templates the mechanism will be created.   You can verify this by looking at the Page Definition/Page Processing/Processes section where there will be an entry name similar to this entry: Process Row of Emp.    If you click on this, it will specify that it is a type Automatic Row Processing (DML).  

You can also add the functionality manually to the form.  For a page, simply go to the Page Definition and add a Process under Page Processing.    Here are the instructions from the User Guide, page 8-21.

To create an Automatic Row Processing (DML) process:
 

1. Navigate to the appropriate Page Definition.

2. Under Processes, click the Create icon.

3. Select the process type Data Manipulation.

4. Select the process category Automatic Row Processing (DML).

5. Specify the following process attributes:

a. In the Name field, type a name to identify the process.

b. In the Sequence field, specify a sequence number.

c. From the Point list, select the appropriate processing point. In most instances,

select Onload - After Header.

d. From the Type list, select Automated Row Processing (DML).

6. Follow the on-screen instructions.

You will also have to make sure you implement two other features:

1.                  Add items and define the Item Source Type as Database Column and specify a case-sensitive column name

2.                  Select the option Always overrides the cache value