A question we are often asked is: what data model or schema changes are allowed on a versioned geodatabase, if any? The answer may surprise a few of you, as there are a lot more modifications allowed than you might think.

In ArcGIS, data model changes can be separated into two categories: minor – such as adding or deleting fields and major – such as removing a feature class from a geometric network.

For the minor data model changes identified below, the participating feature dataset, standalone feature class or table in the geodatabase DOES NOT have to be unversioned. Meaning these changes can be applied with versions remaining in the geodatabase with no impact.

Minor Data Model Changes – NOT Required to Unversion

• Adding or deleting fields
• Adding or deleting simple feature classes (those that do not participate in a topology or geometric network)
• Adding or deleting tables
• Creating or deleting relationship classes
• Creating or deleting attribute domains
• Creating or deleting subtypes
• Changing the default value for an attribute of a given class or subtype
• Changing the attribute domain for an attribute of a given class or subtype
• Creating or deleting indexes for an attribute of a given class
• Altering the spatial index for a given feature class
• Adding an empty feature class to a geometric network
• Adding or removing relationship class rules
• Adding or removing geometric network connectivity rules
• Altering the alias name for classes or fields
• Adding weights to a geometric network (beginning with ArcGIS 9.2)
• Deleting a geometric network
• Renaming or deleting a topology

For the major data model changes identified below, the participating feature dataset, stand-alone feature class or table in the geodatabase MUST be unversioned. In other words, these changes would have considerable impacts on versions and would affect geodatabase performance.

Unversioning the geodatabase requires that (1) all versions to be reconciled and posted to DEFAULT, (2) all versions deleted, and (3) the geodatabase compressed, ensuring all edits in the delta tables are moved to the base tables. Perform these three steps prior to unregistering as versioned the participating feature dataset, standalone feature class or table.

Major Data Model Changes – REQUIRED to Unversion

• Removing weights from a geometric network
• Removing a feature class from a geometric network
• Adding or removing a feature class to a topology
• Adding or removing topology rules
• Altering a topology’s cluster tolerance
• Altering the rank for a feature class in a topology

There are a lot of incorrect assumptions out there about this issue. After reading this article, you should have a better understanding of what data model or schema changes can be applied to a versioned geodatabase, hopefully saving you time when you come across these situations in the future.