Coordinated updates for consistency between servers

In a distributed system, a transaction might occur at more than one server. To ensure data consistency, each subsystem that participates in a single transaction must coordinate update operations. Transactions must be either committed or backed out.

Db2 uses a two-phase commit process with a wide variety of resources, such as relational databases that are accessed through DRDA. Db2 support for two-phase commit can also be used from a number of different application environments. Db2 can work with other z/OS transaction management environments, such as IMS and CICS®, and in UNIX environments, Microsoft Windows applications, and WebSphere® Application Server.

With two-phase commit, you can update a Db2 table and data in non-Db2 databases within the same transaction. The process is under the control of one of the subsystems, called the coordinator. The other systems that are involved are the participants. For example, IMS, CICS, or RRS is always the coordinator in interactions with Db2, and Db2 is always the participant. Db2 is always the coordinator in interactions with TSO and, in that case, completely controls the commit process. In interactions with other DBMSs, including other Db2 subsystems, your local Db2 subsystems can be either the coordinator or a participant.