If an individual task fails, backout is performed automatically by CICS®. If the CICS system fails, backout is performed as part of the auto start process.
However, for long-running programs, it might not be desirable to have a large number of changes, which have accumulated over a period of time, exposed to the possibility of backout if a task or the system fails. You can avoid this possibility by using the EXEC CICS SYNCPOINT command to split the program into logically separate sections that are called logical units of work (LUWs); the end of an LUW is called a synchronization point (syncpoint).
If failure occurs after a syncpoint but before the task has been completed, only changes that were made after the syncpoint are backed out.
LUWs should be entirely logically independent, not merely with regard to protected resources, but also with regard to execution flow. Typically, an LUW comprises a complete conversational operation bounded by EXEC CICS SEND and EXEC CICS RECEIVE commands. A BROWSE is another example of an LUW. An EXEC CICS ENDBR command must therefore precede the syncpoint.