IBM 000-8697 User Manual

IBM Informix OnLine Database Server Administrator’s Guide

Support of two-phase commit requires five additional logical log records.
These records can be used to detect heuristic decisions and, if required, to
help you perform a manual recovery in the event of an inconsistent database
system. The five records and their contents are described in this section. (For
more details about how to display and interpret the contents of the logical
log, refer to

.) The following illustrations of the two-phase commit

protocol are also included in this section:

The

BEGPREP

 logical log record is only written by the coordinator OnLine

database server to record the start of a global transaction.

The output from tblog contains three fields: type, flags, and number of partic-
ipants. The value of the flags is always zero in the

IBM I

nformix

STAR

environment. The number of participants is expressed as an integer. The
output appears as follows:

BEGPREP 0 number_of_participants

The

PREPARE

 logical log record is only written by a participant OnLine

database server to record the ability of the participant to commit the trans-
action, if so instructed.

The output from tblog contains two fields: type and coordinator server name,
specified as the

DBSERVERNAME

. The output appears as follows:

PREPARE coordinator_DBSERVERNAME

shows the logical log records that are written when
a transaction is committed.

shows the logical log records that are written when
a piece of work is heuristically rolled back.

shows the logical log records that are written when
a piece of work is heuristically ended.