Coordinator and Participant in a Distributed Query

To allow cross-server distributed query ability, IBM Informix servers maintain hierarchical relationships consisting of a coordinator and one or more participants. Coordinator and participant are defined as follows:

• The coordinator directs the resolution of the query. It also decides whether the query should be committed or aborted.
• The participant directs the execution of the distributed query on one branch. The branch is the part of the distributed query involving only that participant database server.

The following examples refer to a multi-server environment where db is the local database, db2 is an external database residing on the same server, and master_db is an external database on the remote server new_york.

The following examples shows a query that could be used to access data on another server using database db as the coordinator.

database db; select col1, col2 from db2:tab1, master_db@newyork:tab2;

A session will have only one local database, but can open multiple external databases. Distributed queries must always originate on a coordinator.