Delta Databases

A delta database allows you to make non-permanent (or tentative) changes to an SDS primary database, an SDS secondary database, or an RPS database in read-only mode.

When you activate delta database mode, a new empty database called a delta database is created and the original database, which referred to as the root database, is converted to a read-only state.

When a database is in delta mode:

• All create, update, and delete operations on non-environmental persistent objects are re-directed to the delta database instead of being applied to the root database.

• When the root database is an SDS primary database, updates applied to the delta database are not replicated to any secondary databases.

• Because changes to meta data objects stored in _user*.dat files are not permitted, schema changes cannot be applied.

• When applications access objects are created or updated, they are fetched from the delta database.

• If objects that have been deleted in delta mode are accessed, exception 4 (Object not found) is raised.

The delta database is located in the deltadb subdirectory of the root database path.

When you deactivate delta database mode, the delta database is removed and all updates made in delta mode are discarded.

The delta database can be recovered; that is, if the server node is restarted while the delta database is active, any updates are still present when the node is available again.

To start using delta database functionality, server nodes must be specified to be delta database-capable, by specifying the DeltaDatabaseCapable command with a value of true in the [JadeServer] section of the JADE initialization file on the server node.

Set the ResetDeltaModeOnRestart parameter in the [JadeServer] section to true if on restart, you want the database server node to take the root database out of delta mode and restart in normal mode (that is, to not use the delta database). This effectively results in the contents of the delta database being lost on server restart, as it is always recreated whenever activated. By default, if the database server node is terminated while in delta mode, it attempts to activate the delta database when it restarts.

To activate or deactivate a delta database dynamically from your application logic:

• Call the System class activateDeltaDatabase method with the activate parameter set to true or false, respectively.

• Execute the respective ActivateDeltaDb or DeactivateDeltaDb command in the online JADE Database Administration utility (that is, jdbadmin) from a command script.