Overlays do not perform the following functions:
- Preserving customizations to an object that is deleted during an application upgrade.
If an existing object in your production environment is deleted during an application upgrade, any overlay of the object is also deleted.
Automatically merging customizations with functionality added during upgrades where the customization is in a portion of the overlay that overwrites the origin object.
Granular overlays allow developers to create additive overlays in which they can specify that elements be added to what is inherited from an origin object. These additive overlays do not merge customizations, but they do extend the inherited definitions with the specified additions.
For example, filter actions are part of the Other Definitions portion of a filter overlay that cannot be additive. If that portion of the overlay is overwritten and the filter receives three new actions during an upgrade, those actions are not added to the filter's overlay. Instead, you must identify the new actions by comparing the overlay to the upgraded origin object, and then add the actions to the overlay if you decide to use them.
The form list is a different grain of a filter overlay that can be made additive. In this case, you can specify forms that will be added to the form list that is inherited from the origin filter.
- Enabling you to make all possible changes to BMC Remedy AR System server objects
For example, you cannot make changes that would alter the underlying database, such as changing the data type of the field.