What is an update in a federated system?

In a federated system, an update is not just a transaction that includes an INSERT, UPDATE, or DELETE statement. There are certain operations that are considered updates in a federated system and certain types of updates that are allowed in federated system.

In a federated system, updates can be performed locally or remotely.

Local site updates are updates to tables or views that do not reference nicknames
Remote site updates are updates to objects on a remote data source. Remote data sources include:
- Another database or instance on the federated server
- Another database or instance on another server
- Data sources other than Db2®, such as Db2 for IBM® i, Informix®, Oracle, and Teradata

There are four types of actions that the federated server considers to be update transactions. The following table shows the updates that you can perform on a federated system.

Table 1. Types of updates and the site where the updates are performed
Type of action	Local site	Remote site	Explanation
Local update (DDL and DML)	Y	N	An update on an object in the federated database.
Remote update (nickname)	N	Y	An update on a remote data source object that you created a nickname for.
Dynamic SQL in pass-through sessions	N	Y	An update on a remote data source object. You cannot use a pass-through session to update local objects. Even SELECT queries sent in pass-through sessions are considered to be an update action.
Transparent DDL	Y	Y	A pair of transactions that create, alter, or drop remote tables and their corresponding nicknames in a federated database. For example, a pair of transactions that create a remote table on a data source and a nickname on the federated server.