Externally Coordinated Commit - Teradata Director Program

Teradata® Director Program Reference - 17.20

Deployment
VantageCloud
VantageCore
Edition
Enterprise
IntelliFlex
Lake
VMware
Product
Teradata Director Program
Release Number
17.20
Published
June 2022
Language
English (United States)
Last Update
2023-11-17
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Product Category
Teradata Tools and Utilities

It is possible for a single application to update multiple databases. For example, in a transfer of funds, an application could withdraw money from a bank account on one database and deposit it into another account on a different database. As an option, an application can use an externally coordinated commit process to ensure that updates are applied consistently to all affected databases. One of the methods used to accomplish this process is the Two-phase commit (2PC) protocol, supported by the database.

With the 2PC protocol, an application can update multiple databases in the same logical unit of work, with a coordinator such as IBM’s CICS and IMS transaction processing systems controlling the process. The coordinator uses the 2PC protocol to ensure that all the updates for all the participants in the logical unit of work either commit or roll back. Within a database session that is using the 2PC protocol, there is a time when it is in an in-doubt state, awaiting final instructions from the coordinator on whether to commit or roll back the updates. If a failure in the coordinator or another part of the system occurs during this in-doubt period, the database cannot unilaterally decide to commit or roll back the updates. In the event that automatic in-doubt resolution is not possible because of an extended coordinator outage, manual resolution of the in-doubt sessions can be necessary. This is because these in-doubt sessions can hold locks on database objects that block the progress of other applications that are trying to access those objects.

For more information about Teradata support for IBM’s CICS or IMS interface, see the following documents:
  • IBM CICS Interface for Teradata® Reference, (B035-2448)
  • IBM IMS Interface for Teradata® Reference, B035-2447