Units of work

When resources are being changed, there comes a point when the changes are complete and do not need backout if a failure occurs later. The period between the start of a particular set of changes and the point at which they are complete is called a unit of work (UOW). The unit of work is a fundamental concept of all CICS® backout mechanisms.

From the application designer's point of view, a UOW is a sequence of actions that needs to be complete before any of the individual actions can be regarded as complete. To ensure data integrity, a unit of work must be atomic, consistent, isolated, and durable.

The CICS recovery manager operates with units of work. If a transaction that consists of multiple UOWs fails, or the CICS region fails, committed UOWs are not backed out.

A unit of work can be in one of the following states:

• Active (in-flight)
• Shunted following a failure of some kind
• Indoubt pending the decision of the unit of work coordinator.
• Completed and no longer of interest to the recovery manager