Transaction Processing Synchronization

One program can interact with another program by using one of three levels of synchronization, as shown in Figure A.10:

• Sync Level 0 has no message integrity.
• Sync Level 1 supports limited data integrity.
• Sync Level 2 uses the two-phase commit (2PC) protocol to ensure the reliability of a transaction.

Enlarge figure

Figure A.10 Host TPs Synchronizing Over an APPC Session

Of the three sync levels, only Sync Level 2 guarantees a true ACID-compliant transaction. Thus, in the host environment, the term transaction program might or might not imply the use of Sync Level 2 and the 2PC protocol.

Note

In the Component Object Model (COM) environment, any mention of transactions refers to true ACID-compliant, 2PC transactions.

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