148 lines
7.6 KiB
HTML
148 lines
7.6 KiB
HTML
<!--$Id: db_verify.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
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<!--See the file LICENSE for redistribution information.-->
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<html>
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<head>
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<title>Berkeley DB: Db::verify</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++">
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</head>
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<body bgcolor=white>
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<table width="100%"><tr valign=top>
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<td>
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<b>Db::verify</b>
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</td>
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<td align=right>
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<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a>
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<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
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</tr></table>
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<hr size=1 noshade>
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<tt>
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<b><pre>
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#include <db_cxx.h>
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<p>
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int
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Db::verify(const char *file,
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const char *database, ostream *outfile, u_int32_t flags);
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</pre></b>
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<hr size=1 noshade>
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<b>Description: Db::verify</b>
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<p>The Db::verify method verifies the integrity of all databases in the
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file specified by the <b>file</b> parameter, and optionally outputs the
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databases' key/data pairs to the file stream specified by the
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<b>outfile</b> parameter.</p>
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<p><b>The Db::verify method does not perform any locking, even in Berkeley DB
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environments that are configured with a locking subsystem. As such, it
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should only be used on files that are not being modified by another
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thread of control.</b></p>
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<p>The Db::verify method may not be called after the <a href="../api_cxx/db_open.html">Db::open</a> method is called.
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</p>
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<p>The <a href="../api_cxx/db_class.html">Db</a> handle may not be accessed again after Db::verify is
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called, regardless of its return.</p>
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<a name="2"><!--meow--></a>
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<p>The Db::verify method will return DB_VERIFY_BAD if a database is
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corrupted. When the DB_SALVAGE flag is specified, the
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DB_VERIFY_BAD return means that all key/data pairs in the file
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may not have been successfully output.
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Unless otherwise specified, the Db::verify method
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either returns a non-zero error value
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or throws an exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>database</b><ul compact><li>The <b>database</b> parameter is the database in <b>file</b> on which
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the database checks for btree and duplicate sort order and for hashing
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are to be performed. See the DB_ORDERCHKONLY flag for more
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information.
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<p>The database parameter must be set to NULL except when the
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DB_ORDERCHKONLY flag is set.</p></ul>
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<b>file</b><ul compact><li>The <b>file</b> parameter is the physical file in which the databases
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to be verified are found.</ul>
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<b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or
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the following value:
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<br>
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<b><a name="DB_SALVAGE">DB_SALVAGE</a></b><ul compact><li>Write the key/data pairs from all databases in the file to the file
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stream named in the <b>outfile</b> parameter. Key values are written
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for Btree, Hash and Queue databases, but not for Recno databases.
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<p>The output format is the same as that specified for the <a href="../utility/db_dump.html">db_dump</a>
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utility, and can be used as input for the <a href="../utility/db_load.html">db_load</a> utility.</p>
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<p>Because the key/data pairs are output in page order as opposed to the sort
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order used by <a href="../utility/db_dump.html">db_dump</a>, using Db::verify to dump key/data
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pairs normally produces less than optimal loads for Btree databases.</p></ul>
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<br>
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<p>In addition, the following flags may be set by bitwise inclusively <b>OR</b>'ing them into the
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<b>flags</b> parameter:</p>
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<br>
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<b><a name="DB_AGGRESSIVE">DB_AGGRESSIVE</a></b><ul compact><li>Output <b>all</b> the key/data pairs in the file that can be found.
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By default, Db::verify does not assume corruption. For example,
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if a key/data pair on a page is marked as deleted, it is not then written
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to the output file. When DB_AGGRESSIVE is specified, corruption
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is assumed, and any key/data pair that can be found is written. In this
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case, key/data pairs that are corrupted or have been deleted may appear
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in the output (even if the file being salvaged is in no way corrupt), and
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the output will almost certainly require editing before being loaded into
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a database.</ul>
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<b><a name="DB_PRINTABLE">DB_PRINTABLE</a></b><ul compact><li>When using the DB_SALVAGE flag, if characters in either the key
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or data items are printing characters (as defined by <b>isprint</b>(3)), use printing characters to represent them. This flag permits users
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to use standard text editors and tools to modify the contents of
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databases or selectively remove data from salvager output.
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<p>Note: different systems may have different notions about what characters
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are considered <i>printing characters</i>, and databases dumped in
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this manner may be less portable to external systems.</p></ul>
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<b><a name="DB_NOORDERCHK">DB_NOORDERCHK</a></b><ul compact><li>Skip the database checks for btree and duplicate sort order and for
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hashing.
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<p>The Db::verify method normally verifies that btree keys and duplicate
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items are correctly sorted, and hash keys are correctly hashed. If the
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file being verified contains multiple databases using differing sorting
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or hashing algorithms, some of them must necessarily fail database
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verification because only one sort order or hash function can be
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specified before Db::verify is called. To verify files with
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multiple databases having differing sorting orders or hashing functions,
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first perform verification of the file as a whole by using the
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DB_NOORDERCHK flag, and then individually verify the sort order
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and hashing function for each database in the file using the
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DB_ORDERCHKONLY flag.</p></ul>
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<b><a name="DB_ORDERCHKONLY">DB_ORDERCHKONLY</a></b><ul compact><li>Perform the database checks for btree and duplicate sort order and for
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hashing, skipped by DB_NOORDERCHK.
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<p>When this flag is specified, a <b>database</b> parameter should also be
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specified, indicating the database in the physical file which is to be
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checked. This flag is only safe to use on databases that have already
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successfully been verified using Db::verify with the
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DB_NOORDERCHK flag set.</p></ul>
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<br></ul>
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<b>outfile</b><ul compact><li>The <b>outfile</b> parameter is an optional file stream to which the
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databases' key/data pairs are written.</ul>
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<br>
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<br><b>Environment Variables</b>
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<p>If the database was opened within a database environment, the
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environment variable <b>DB_HOME</b> may be used as the path of the
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database environment home.</p>
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<p>Db::verify is affected by any database directory specified using
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the <a href="../api_cxx/env_set_data_dir.html">DbEnv::set_data_dir</a> method, or by setting the "set_data_dir" string
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in the environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file.</p>
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<br><b>Errors</b>
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<br>
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<b>ENOENT</b><ul compact><li>The file or directory does not exist.</ul>
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<br>
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<p>The Db::verify method
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may fail and throw
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<a href="../api_cxx/except_class.html">DbException</a>,
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encapsulating one of the following non-zero errors, or return one of
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the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>If Db::verify was called after <a href="../api_cxx/db_open.html">Db::open</a>; or if an
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_cxx/db_class.html">Db</a>
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<br><b>See Also</b>
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<a href="../api_cxx/db_list.html">Databases and Related Methods</a>
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</tt>
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<table width="100%"><tr><td><br></td><td align=right>
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<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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</body>
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</html>
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