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libdb/docs/api_reference/CXX/logarchive.html
Gregory Burd 940129b94f Release 5.2.36 on 9/14/2022
2011-12-19 19:07:10 -05:00

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<th colspan="3" align="center">DbEnv::log_archive()</th>
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<tr>
<td width="20%" align="left"><a accesskey="p" href="envget_lg_regionmax.html">Prev</a> </td>
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The DbLsn Handle
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<div class="sect1" lang="en" xml:lang="en">
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<h2 class="title" style="clear: both"><a id="logarchive"></a>DbEnv::log_archive()</h2>
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<pre class="programlisting">#include &lt;db_cxx.h&gt;
int
DbEnv::log_archive(char *(*listp)[], u_int32_t flags);</pre>
<p>
The <code class="methodname">DbEnv::log_archive()</code> method returns an array of log or database
filenames.
</p>
<p>
By default, <code class="methodname">DbEnv::log_archive()</code> returns the names of all of the
log files that are no longer in use (for example, that are no longer involved in active
transactions), and that may safely be archived for catastrophic recovery and then removed
from the system. If there are no filenames to return, the memory location to which
<span class="bold"><strong>listp</strong></span> refers will be set to NULL.
</p>
<p>
When Replication Manager is in use, log archiving is
performed in a replication group-aware manner such that the
log file status of other sites in the group is considered to
determine if a log file is in use.
</p>
<p>
Arrays of log filenames are stored in allocated memory. If application-specific allocation
routines have been declared (see <a class="xref" href="envset_alloc.html" title="DbEnv::set_alloc()">DbEnv::set_alloc()</a>
for more information), they are used to allocate the memory; otherwise, the standard
C library <span class="bold"><strong>malloc</strong></span>(3) is used. The caller is responsible
for deallocating the memory. To deallocate the memory, free the memory reference;
references inside the returned memory need not be individually freed.
</p>
<p>
Log cursor handles (returned by the <a class="xref" href="logcursor.html" title="DbEnv::log_cursor()">DbEnv::log_cursor()</a>
method) may have open file descriptors for log files in the database environment. Also,
the Berkeley DB interfaces to the database environment logging subsystem (for example,
<a class="xref" href="logput.html" title="DbEnv::log_put()">DbEnv::log_put()</a> and <a class="xref" href="txnabort.html" title="DbTxn::abort()">DbTxn::abort()</a> ) may allocate log cursors and have open file descriptors
for log files as well. On operating systems where filesystem related system calls (for
example, rename and unlink on Windows/NT) can fail if a process has an open file descriptor
for the affected file, attempting to move or remove the log files listed by
<code class="methodname">DbEnv::log_archive()</code> may fail. All Berkeley DB internal use of log
cursors operates on active log files only and furthermore, is short-lived in nature. So,
an application seeing such a failure should be restructured to close any open log cursors
it may have, and otherwise to retry the operation until it succeeds. (Although the latter
is not likely to be necessary; it is hard to imagine a reason to move or rename a log file
in which transactions are being logged or aborted.)
</p>
<p>
See <a class="link" href="db_archive.html" title="db_archive">db_archive</a> for more information on
database archival procedures.
</p>
<p>
The <code class="methodname">DbEnv::log_archive()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id3618208"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3618198"></a>listp</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>listp</strong></span> parameter references memory
into which the allocated array of log or database filenames is copied.
If there are no filenames to return, the memory location to which
<span class="bold"><strong>listp</strong></span> refers will be set to NULL.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3617848"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
or by bitwise inclusively <span class="bold"><strong>OR</strong></span>'ing
together one or more of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="archive_DB_ARCH_ABS"></a>
<code class="literal">DB_ARCH_ABS</code>
</p>
<p>
All pathnames are returned as absolute pathnames, instead of relative
to the database home directory.
</p>
</li>
<li>
<p><a id="archive_DB_ARCH_DATA"></a>
<code class="literal">DB_ARCH_DATA</code>
</p>
<p>
Return the database files that need to be archived in order to recover
the database from catastrophic failure. If any of the database files
have not been accessed during the lifetime of the current log files,
<code class="methodname">DbEnv::log_archive()</code> will not include them in this list. It is also
possible that some of the files referred to by the log have since been
deleted from the system.
</p>
<p>
The <code class="literal">DB_ARCH_DATA</code> and <code class="literal">DB_ARCH_LOG flags</code> are mutually exclusive.
</p>
</li>
<li>
<p><a id="archive_DB_ARCH_LOG"></a>
<code class="literal">DB_ARCH_LOG</code>
</p>
<p>
Return all the log filenames, regardless of whether or not they are in
use.
</p>
<p>
The <code class="literal">DB_ARCH_DATA</code> and <code class="literal">DB_ARCH_LOG flags</code> are mutually exclusive.
</p>
</li>
<li>
<p><a id="archive_DB_ARCH_REMOVE"></a>
<code class="literal">DB_ARCH_REMOVE</code>
</p>
<p>
Remove log files that are no longer needed; no filenames are returned.
Automatic log file removal is likely to make catastrophic recovery
impossible.
</p>
<p>
The <code class="literal">DB_ARCH_REMOVE</code> flag may not be specified with any other flag.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id3618525"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbEnv::log_archive()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3618433"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
An invalid flag value or parameter was specified.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id3618601"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5.  The DbEnv Handle">DbEnv</a>,
<a class="link" href="logc.html" title="The DbLogc Handle">DbLogc</a>,
<a class="link" href="lsn.html" title="Chapter 8.  The DbLsn Handle">DbLsn</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id3618195"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="lsn.html#loglist" title="Logging Subsystem and Related Methods">Logging Subsystem and Related Methods</a>
</p>
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