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Import BSDDB 4.7.25 (as of svn r89086)

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Zachary Ware
2017-09-04 13:40:25 -05:00
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<H2>
<A NAME="Logging Commands"></A>Logging Commands</H2>
Logging commands work from the environment handle to control the use of
the log files.&nbsp; Log files are opened when the environment is opened
and closed when the environment is closed.&nbsp; In all of the commands
in the logging subsystem that take or return a log sequence number, it
is of the form:
<BR><B>{<I>fileid offset</I>}</B>
<BR>where the <B><I>fileid</I></B> is an identifier of the log file, as
returned from the <A HREF="#> <env> log_get">log_get</A> call.
<P><B>> &lt;env> log_archive [-arch_abs] [-arch_data] [-arch_log]</B>
<P>This command returns&nbsp; a list of log files that are no longer in
use.&nbsp; It is a direct call to the <A HREF="../../docs/api_c/log_archive.html">log_archive</A>
function. The arguments are:
<UL>
<LI>
<B>-arch_abs </B>selects DB_ARCH_ABS to return all pathnames as absolute
pathnames</LI>
<LI>
<B>-arch_data </B>selects DB_ARCH_DATA to return a list of database files</LI>
<LI>
<B>-arch_log </B>selects DB_ARCH_LOG to return a list of log files</LI>
</UL>
<HR WIDTH="100%">
<BR><B>> &lt;env> log_compare <I>lsn1 lsn2</I></B>
<P>This command compares two log sequence numbers, given as <B><I>lsn1</I></B>
and <B><I>lsn2</I></B>.&nbsp; It is a direct call to the <A HREF="../../docs/api_c/log_compare.html">log_compare</A>
function.&nbsp; It will return a -1, 0, 1 to indicate if <B><I>lsn1</I></B>
is less than, equal to or greater than <B><I>lsn2</I></B> respectively.
<BR>
<HR WIDTH="100%">
<BR><B>> &lt;env> log_file <I>lsn</I></B>
<P>This command returns&nbsp; the file name associated with the given <B><I>lsn</I></B>.&nbsp;
It is a direct call to the <A HREF="../../docs/api_c/log_file.html">log_file</A>
function.
<BR>
<HR WIDTH="100%">
<BR><B>> &lt;env> log_flush [<I>lsn</I>]</B>
<P>This command&nbsp; flushes the log up to the specified <B><I>lsn</I></B>
or flushes all records if none is given&nbsp; It is a direct call to the
<A HREF="../../docs/api_c/log_flush.html">log_flush</A>
function.&nbsp; It returns either a 0 (for success), a DB error message
or it throws a Tcl error with a system message.
<BR>
<HR WIDTH="100%">
<BR><A NAME="<env> log_get"></A><B>> &lt;env> log_get<I> </I>[-checkpoint]
[-current] [-first] [-last] [-next] [-prev] [-set <I>lsn</I>]</B>
<P>This command retrieves a record from the log according to the <B><I>lsn</I></B>
given and returns it and the data.&nbsp; It is a direct call to the <A HREF="../../docs/api_c/log_get.html">log_get</A>
function.&nbsp; It is a way of implementing a manner of log iteration similar
to <A HREF="../../docs/api_tcl/db_cursor.html">cursors</A>.&nbsp;&nbsp;
The information we return is similar to database information.&nbsp; We
return a list where the first item is the LSN (which is a list itself)
and the second item is the data.&nbsp; So it looks like, fully expanded,
<B>{{<I>fileid</I>
<I>offset</I>}
<I>data</I>}.</B>&nbsp;
In the case where DB_NOTFOUND is returned, we return an empty list <B>{}</B>.&nbsp;
All other errors return a Tcl error.&nbsp; The arguments are:
<UL>
<LI>
<B>-checkpoint </B>selects the DB_CHECKPOINT flag to return the LSN/data
pair of the last record written through <A HREF="#> <env> log_put">log_put</A>
with DB_CHECKPOINT specified</LI>
<LI>
<B>-current</B> selects the DB_CURRENT flag to return the current record</LI>
<LI>
<B>-first</B> selects the DB_FIRST flag to return the first record in the
log.</LI>
<LI>
<B>-last </B>selects the DB_LAST flag to return the last record in the
log.</LI>
<LI>
<B>-next</B> selects the DB_NEXT flag to return the next record in the
log.</LI>
<LI>
<B>-prev </B>selects the DB_PREV flag to return the&nbsp; previous record
in the log.</LI>
<LI>
<B>-set</B> selects the DB_SET flag to return the record specified by the
given <B><I>lsn</I></B></LI>
</UL>
<HR WIDTH="100%">
<BR><A NAME="> <env> log_put"></A><B>> &lt;env> log_put<I> </I>[-checkpoint]
[-flush] <I>record</I></B>
<P>This command stores a <B><I>record</I></B> into the log and returns
the LSN of the log record.&nbsp; It is a direct call to the <A HREF="../../docs/api_c/log_put.html">log_put</A>
function.&nbsp; It returns either an LSN or it throws a Tcl error with
a system message.&nbsp;<B> </B>The arguments are:
<UL>
<LI>
<B>-checkpoint </B>selects the DB_CHECKPOINT flag</LI>
<LI>
<B>-flush </B>selects the DB_FLUSH flag to flush the log to disk.</LI>
</UL>
<HR WIDTH="100%">
<BR><B>> &lt;env> log_stat</B>
<P>This command returns&nbsp; the statistics associated with the logging
subsystem.&nbsp; It is a direct call to the <A HREF="../../docs/api_c/log_stat.html">log_stat</A>
function.&nbsp; It returns a list of name/value pairs of the DB_LOG_STAT
structure.
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