IBM 000-8697 Manuale Utente
9-46
IBM Informix OnLine Database Server Administrator’s Guide
Two-Phase Commit and Logical Log Records
The output from tblog contains only the type field, as follows:
ENDTRANS
Transaction Commit Records
illustrates the writing sequence of the logical log records during
a successful two-phase commit protocol that results in a committed trans-
action. (Refer to
action. (Refer to
for a more general discussion of this same
illustration.)
Some of the logical log records must be flushed immediately; for others,
flushing is not critical. The explanation of this difference follows the figure.
flushing is not critical. The explanation of this difference follows the figure.
Figure 9-10
Logical log records
written during a
two-phase commit
protocol that
results in a
committed
transaction
All Participants:
Write log record: TABLOCKS.
Write and flush log record: PREPARE.
Send message: “can commit.”
Write log record: TABLOCKS.
Write and flush log record: PREPARE.
Send message: “can commit.”
Coordinator:
Writes log record: ENDTRANS.
Writes log record: ENDTRANS.
Coordinator:
Writes log record: BEGPREP.
Sends message: “precommit.”
Writes log record: BEGPREP.
Sends message: “precommit.”
All Participants:
Write and flush log record: COMMIT.
Send message: “committed.”
Write and flush log record: COMMIT.
Send message: “committed.”
Coordinator:
Writes and flushes log record: COMMIT.
Sends message: “commit.”
Writes and flushes log record: COMMIT.
Sends message: “commit.”
End Protocol
Start Protocol
P
C
C
P
C
P
P
P
P