IBM 000-8697 Bedienungsanleitung Seite 296

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3-40 IBM Informix OnLine Database Server Administrator’s Guide
Free a Logical Log File
Refertopage 3-15fora discussionabouttheimportanceoffreeingthelogical
log files in a timely manner. Refer to page 3-26 for information about the
logical log file status flags. Refer to page 3-27 for more information about
how the logical log files rotate through ID numbers.
OnLine user processes attempt to free logical log files under the following
conditions:
The first OnLine user process that writes to a new logical log file
attempts to free the previous log.
Eachtimetbtapecompletesitsbackupofalogicallogfile,itattempts
to free the log file.
Each time an OnLine database server process commits or rolls back
atransaction, it attemptsto freethe logical log fileinwhichthetrans-
action began.
EachtimeanOnLineuserprocessattemptstousethenextlogicallog
file, it attempts to free the log file, if it is not already free.
Long Transactions
A long transaction is an open transaction that starts in the first logical log file
(theonewiththelowestIDnumberatanytime).Sincealogicallogfilecannot
be freed until all records within the file are associated with closed transac-
tions, the long transaction prevents the first logical log file from becoming
free and available for reuse. The logged data must be kept intact (not
overwritten) in case the open transaction must be rolled back.
Ifalongtransactionwerepermittedtocontinue,itcouldposeathreattoyour
OnLine processing. If OnLine attempted to fill the next logical log file in
sequence but found that it was unreleased (status U) and not freed, OnLine
processing would be suspended to protect the data in the logical log file.
Long transactions are handled automatically by OnLine. For further infor-
mation about how OnLine handles long transactions internally, refer to the
discussion of the LTXHWM and LTXEHWM configuration file parameters on
page 2-159.
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