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9-50 IBM Informix OnLine Database Server Administrator’s Guide
Two-Phase Commit and Logical Log Records
Heuristic End-Transaction Records
Figure 9-12 illustrates the writing sequence of the logical log records during
a heuristic end-transaction. The event is always the result of an administrator
executing tbmode -Z at a participant OnLine database server after the partic-
ipant has sent a message: “can commit.” (Refer to page 9-40 for a description
of a heuristic end-transaction.) In Figure 9-12, the heuristic end-transaction is
assumed to have occurred at the P1 participant.
Important: The transaction is inconsistently implemented.
Figure 9-12
Writes of
logical log records
during a heuristic
end-
transaction
All Participants:
Writes log record: TABLOCKS.
Writes and flushes log record: PREPARE.
Sends message: “commit ok.”
Coordinator:
Writes log record: BEGPREP.
Sends message: “precommit.”
P1 Participant:
Sends message: “Transaction status unknown.”
Coordinator:
Writes and flushes log record: COMMIT.
Sends message: “commit.”
Within P1 Participant’s Environment:
tbmode -Z is executed.
Writes log record: ROLLBACK.
Writes log record: ENDTRANS.
Message is written in OnLine message log.
Start Protocol
Transaction is
inconsistently implemented
Coordinator:
Assumes “unknown” status means “committed.”
Writes log record: ENDTRANS.
P2 and P3 Participants:
Send message: “committed.”
C
P1
C
P2 P3
P1 P2 P3
C