A virtual data model has three layouts: Source Layout, Virtual Entity Layout, and Cache Db Layout. You can see the first two layouts by opening the properties of an entity. The Cache Db Layout is only visible if you have selected the Cache Enabled option from the context menu. You can access this layout by opening cache properties.
A virtual data model allows the user to add heterogeneous sources. Therefore, for each type of added source, the Source Layout will vary accordingly. The Source Layout will have all the attributes present in general for the respective Centerprise sources. You may modify the layout by adding or deleting field and modifying existing ones. If you have modified the Source Layout, you will have to refresh the Virtual Entity Layout, which will appear as you navigate to the next page.
Virtual Entity Layout
This layout will be visible to users after a virtual data model is deployed. When you use a Multi-Table Query Source and connect it to Astera Data Model (ADM) database provider, you will be able to see the Virtual Entity Layout. The Db Type is the database type that is specific to ADM data types only.
Cache Db Layout
Astera Data Virtualization supports building cache database for entities to enhance query performance, reduce execution time, and save cost incurred on accessing the sources directly. The Virtual Entity Cache Db Layout represents the entities in a cache database. To enable the Cache Db Layout, you will have to right click on an entity and select Cache Enabled. On opening the Cache Properties, you will first see the Virtual Entity Layout. This is for comparing the Virtual Entity Layout with the Cache Db Layout. If you have changed the Source Layout, you will have to refresh the Cache Db Layout to visualize those changes.
There are two ways to refresh the layouts:
1. By right-clicking the entity: On using the context menu option, all the changes that have been made to the layouts in the properties will be reverted, and the entities will be re-synchronized with the source.
2. From the properties screen: Refreshing the Source Layout from the properties screen will restore the source to its previous layout. In case you want to reflect the Source Layout changes in Virtual Entity and Cache Db Layout, you will have to go to the layout screen in the properties wizard and click on refresh.