Transforms › Work with Nested Transforms

Work with Nested Transforms

When you apply a transform to an existing transform, you create a nested transform. Some examples of nested transforms are:

• When you create one or more supertype-subtype rollup transforms, then apply a horizontal or vertical partition transform to the resulting table.
• When you create a two-table denormalization rollup or rolldown transform, then apply a horizontal or vertical partition transform to the resulting table.

You can also apply transforms consecutively, to create a nested transform. Transforms can only be nested in a sequential order. If you want to add a new transform that would be based on some objects already involved in another transform, then the first transform has to be in target mode. The target objects of the first transform become the source objects for the next transform.

Important: When you attempt to apply a new transform on some source objects of an existing transform then the corresponding toolbar buttons are disabled. However, if you switch the first transform to be showing targets then the toolbar buttons become enabled as the new transform is now allowed.

You can work with nested transforms in the same way you work with single transforms. You can do the following:

• Use the transform wizard to complete the steps necessary to create the nested transform.
• Nested Transform results are displayed in the Model Explorer in the Transform tree. You can use the Model Explorer to display the list of source and target objects associated with the nested transform.
• Reverse a nested transform. When you reverse a transform, you preserve the source objects while deleting the transform and the model objects that the transform creates.

  Note: you must reverse nested transforms in the reverse order in which they were created. Reverse the transform you created last, then work back through the related transforms. In the Model Explorer, right-click the transform that you want to reverse, choose Delete, then choose Reverse.

• Resolve a nested transform. When you resolve a nested transform, you preserve the model objects that the transform creates and delete the source objects and the transform itself. In the Model Explorer, right-click the transform that you want to resolve, choose Delete, then choose Resolve.

Important: If your model with nested transforms is checked out of CA ERwin Model Manager, exercise caution when resolving transforms in the model. When you save a modified model to the mart, you can undo changes using the Difference Reconciliation dialog. Be aware that if you undo changes after resolving a transform, the resulting model may not be the same as before the transform was applied. We recommend that you save your changes to the database before resolving a nested transform.

More information:

Transforms in the Model Explorer

Display or Hide the Transforms Toolbar

Refine a Model Using Transforms

Apply a Transform

Display Options for Transforms

Delete a Transform