To a client application, versioned data appears much the same as unversioned data: versioned tables and feature classes look like the unversioned tables and feature classes. A table or feature class viewed in one version will contain a certain number of rows, and the same table or feature class in another version may contain a different number of rows, giving the impression that each version is a separate copy of the data.

However, instead of creating a new copy of, or modifying the original data, the geodatabase leaves the versioned table or feature class in its original form and stores any changes to that data in separate geodatabase system tables. The geodatabase system tables that record version changes are referred to as the delta tables. For each table or feature class that has been versioned, two new delta tables, an Adds and a Deletes table, are created.

These delta tables record any changes (new, modified, or deleted records) made to that table or feature class at each state of the database. To correctly represent each database version, these tables are queried, in conjunction with the Versions and State_Lineages tables, to identify which change was made at which database state. A version will then return a seamless view of the data that takes into account the original state of the data plus any changes.

Adds Table - A<Registration_ID> (+/-)

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The Adds table stores all additions and modifications to the base table. This table has the same schema as the base table with the addition of the SDE_state_ID column. Thus, the Adds table maintains a copy of each row inserted into the table under a specific state. Each column in the base table is duplicated in the addition table. The SDE_state_ID column indicates the state the row was added for; the Row_ID (or ObjectID) column is already defined in the base table schema and has been repeated here for emphasis. The Row_ID column is named as defined by the TABLE_REGISTRY entry for each versioned table.

The Adds table has the following columns:

Column Name	Description
SDE_state_ID	The state to which the feature belongs
row_id OR ObjectID	The unique identifier for the row
other columns	Existing columns in the table

 

Deletes Table - D<Registration_ID> (+/-)

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For each versioned table in the database, there is an associated deletion table. This table is named D<registration_id> and is created when versioning is enabled on the table. The Deletes table stores all deleted and modified row references and thus maintains a list of all features that are deleted or modified in the versioned table; SDE_state_ID and SDE_Deletes_Row_ID form a unique key for the feature or row to be deleted. The Deleted_At indicates the state that is requesting the modification.

The Deletes table has the following columns:

Column Name	Description
SDE_state_ID	The state from which the row is being deleted
SDE_Deletes_Row_ID	The unique ID of the row being updated or deleted
Deleted_At	The state that is making the modification

 

Version View (+/-)

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The versioned view is optional and reconstructs the contents of the versioned table for a specified version of the database. This view is what applications other than ArcSDE will see as the versioned table, and should have a descriptive name. This view is constructed from a set a queries and SQL packages that use the base, additions, and deletions table for data.

Applications access the versioned view by setting the desired version in the database using the supplied SQL Stored Procedure sde_version_util.set_current_version ('version name') function in the ArcSDE client library. Once set, all operations will be against the specified version of the database. If no version is set using this function, the DEFAULT version will be used. See ArcGIS Server or ArcGIS Desktop help topic What are multiversioned views for stored procedure names and syntax for your DBMS.