Diagram partitioning can be used to reduce the number of elements in a diagram to make it easier to work with when the number of elements - tables and relations - on a single diagram grows considerably.


Diagram partitioning is automatically used when multiple databases are hosted in a single diagram file or when database areas are defined, apart that the use can create any number of 'logical' partitions to either simply group diagram elements in smaller, more manageable sections or to focus on a specific area of interest.


The elements that can be used for diagram partitioning are:


Database

It corresponds to a physical database, it can only be created in the main diagram (root database) and contains any other diagram objects apart from database.

Area

It corresponds to a physical database area, it can only be created in a database diagram (including the root database) and can contain only tables and relations.

Partition

It's just a logical view, same as database areas can only be created in a database diagram and can contain tables and relations only.


Since all those elements have a diagram attached the corresponding diagram can be open in a separate editor page by simply doing a double-click on the element, the newly open editor will show the exact location (URL) of the diagram in the title bar - first the diagram file as for the main diagram followed by the hash (#) separator then relative path of partition within the diagram file. The relative path is created using the names of partitions separated by slash (/), given the restrictions on partition nesting the relative path can have at most two segments.


When diagram partitioning is used a diagram partition normally only shows the tables that are defined in it but since it is just a logical view tables from other partitions can be included in the view by creating shortcuts - those tables will have a shortcut decorator in the left-lower corner.




Because all editors work with the same resource - diagram file - making changes in different diagram sections is not supported as saving changes in one editor might override the changes still not saved on another editor page open on the same file. When saving changes on one editor other editor(s) open on the same diagram tree will detect changes were made outside of the editor and prompt to reload the diagram to reflect those changes.



If you choose to ignore that and keep the current changes when trying to save the changes later the update conflict will be detected and a new prompt will ask for confirmation to override any previously saved changes so those are effectively lost and no reconciliation is being attempted to synchronize the changes.