Berkeley DB: Db::verify
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++

### Db::verify |

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###

    #include <db_cxx.h>

    int
    Db::verify(const char *file,
        const char *database, ostream *outfile, u_int32_t flags);

### Description: Db::verify

The Db::verify method verifies the integrity of all databases in the file specified by the file parameter, and optionally outputs the databases' key/data pairs to the file stream specified by the outfile parameter.

The Db::verify method does not perform any locking, even in Berkeley DB environments that are configured with a locking subsystem. As such, it should only be used on files that are not being modified by another thread of control.

The Db::verify method may not be called after the Db::open method is called.

The Db handle may not be accessed again after Db::verify is called, regardless of its return.

The Db::verify method will return DB_VERIFY_BAD if a database is corrupted. When the DB_SALVAGE flag is specified, the DB_VERIFY_BAD return means that all key/data pairs in the file may not have been successfully output. Unless otherwise specified, the Db::verify 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.

### Parameters

database
  The database parameter is the database in file on which the database checks for btree and duplicate sort order and for hashing are to be performed. See the DB_ORDERCHKONLY flag for more information.

  The database parameter must be set to NULL except when the DB_ORDERCHKONLY flag is set.

file
  The file parameter is the physical file in which the databases to be verified are found.
flags
  The flags parameter must be set to 0 or the following value:
  DB_SALVAGE
    Write the key/data pairs from all databases in the file to the file stream named in the outfile parameter. The output format is the same as that specified for the db_dump utility, and can be used as input for the db_load utility.

    Because the key/data pairs are output in page order as opposed to the sort order used by db_dump, using Db::verify to dump key/data pairs normally produces less than optimal loads for Btree databases.

  In addition, the following flags may be set by bitwise inclusively OR'ing them into the flags parameter:

  DB_AGGRESSIVE
    Output all the key/data pairs in the file that can be found. By default, Db::verify does not assume corruption. For example, if a key/data pair on a page is marked as deleted, it is not then written to the output file. When DB_AGGRESSIVE is specified, corruption is assumed, and any key/data pair that can be found is written. In this case, key/data pairs that are corrupted or have been deleted may appear in the output (even if the file being salvaged is in no way corrupt), and the output will almost certainly require editing before being loaded into a database.
  DB_PRINTABLE
    When using the DB_SALVAGE flag, if characters in either the key or data items are printing characters (as defined by isprint(3)), use printing characters to represent them. This flag permits users to use standard text editors and tools to modify the contents of databases or selectively remove data from salvager output.

    Note: different systems may have different notions about what characters are considered printing characters, and databases dumped in this manner may be less portable to external systems.

  DB_NOORDERCHK
    Skip the database checks for btree and duplicate sort order and for hashing.

    The Db::verify method normally verifies that btree keys and duplicate items are correctly sorted, and hash keys are correctly hashed. If the file being verified contains multiple databases using differing sorting or hashing algorithms, some of them must necessarily fail database verification because only one sort order or hash function can be specified before Db::verify is called. To verify files with multiple databases having differing sorting orders or hashing functions, first perform verification of the file as a whole by using the DB_NOORDERCHK flag, and then individually verify the sort order and hashing function for each database in the file using the DB_ORDERCHKONLY flag.

  DB_ORDERCHKONLY
    Perform the database checks for btree and duplicate sort order and for hashing, skipped by DB_NOORDERCHK.

    When this flag is specified, a database parameter should also be specified, indicating the database in the physical file which is to be checked. This flag is only safe to use on databases that have already successfully been verified using Db::verify with the DB_NOORDERCHK flag set.

outfile
  The outfile parameter is an optional file stream to which the databases' key/data pairs are written.

### Environment Variables

If the database was opened within a database environment, the environment variable DB_HOME may be used as the path of the database environment home.

Db::verify is affected by any database directory specified using the DbEnv::set_data_dir method, or by setting the "set_data_dir" string in the environment's DB_CONFIG file.

### Errors

ENOENT
  The file or directory does not exist.

The Db::verify method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:

EINVAL
  If Db::verify was called after Db::open; or if an invalid flag value or parameter was specified.

### Class

Db

### See Also

Databases and Related Methods`

Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.