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<chapter id="wal">

<title>Write-Ahead Logging (<acronym>WAL</acronym>)</title>

</para>

<para>

The <varname>COMMIT_DELAY</varname> parameter defines for howlong

the backend willbe forced tosleep after writing a commit record

to the log with <function>LogInsert</function> call but before

The <varname>COMMIT_DELAY</varname> parameter defines for howmany

microsecondsthe backend will sleep after writing a commit

recordto the log with <function>LogInsert</function> but before

performing a <function>LogFlush</function>. This delay allows other

backends to add their commit records to the log so as to have all

of them flushed with a single log sync. Unfortunately, this

mechanism is not fully implemented at release 7.1, so there is at

present nopoint in changing this parameterfromits default value

of 5 microseconds.

presentusuallynobenefit to be gainedfromincreasing this parameter

above its default value of zero.

</para>

</sect1>

</chapter>

intCommitDelay=5;/*1/200000 sec */

intCommitDelay=0;/*in microseconds */

staticvoid (*_RollbackFunc)(void*)=NULL;

staticvoid*_RollbackData=NULL;

{

XLogRecDatardata;

xl_xact_commitxlrec;

structtimevaldelay;

XLogRecPtrrecptr;

BufmgrCommit();

delay.tv_sec=0;

delay.tv_usec=CommitDelay;

(void)select(0,NULL,NULL,NULL,&delay);

if (CommitDelay>0)

{

structtimevaldelay;

delay.tv_sec=0;

delay.tv_usec=CommitDelay;

(void)select(0,NULL,NULL,NULL,&delay);

}

XLogFlush(recptr);

MyLastRecPtr.xrecoff=0;

0,0,16},

{"commit_delay",PGC_USERSET,&CommitDelay,

5,0,1000},

0,0,100000},

{NULL,0,NULL,0,0,0}

};

#wal_buffers = 8 # min 4

#wal_files = 0 # range 0-64

#wal_debug = 0 # range 0-16

#commit_delay =5 # range 0-1000

#commit_delay =0 # range 0-100000

#checkpoint_timeout = 300 # range 30-1800