Berkeley DB: DbEnv.log_archive
Description: Berkeley DB: An embedded database programmatic toolkit.
Keywords: embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++

# DbEnv.log_archive |

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    import com.sleepycat.db.*;

    public String[] log_archive(int flags)
        throws DbException;

# Description

The DbEnv.log_archive method returns an array of log or database filenames.

By default, DbEnv.log_archive 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, DbEnv.log_archive returns null.

The flags value must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:

Db.DB_ARCH_ABS
  All pathnames are returned as absolute pathnames, instead of relative to the database home directory.

Db.DB_ARCH_DATA
  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, DbEnv.log_archive 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.

Db.DB_ARCH_LOG
  Return all the log filenames, regardless of whether or not they are in use.

The Db.DB_ARCH_DATA and Db.DB_ARCH_LOG flags are mutually exclusive.

Log cursor handles (returned by the DbEnv.log_cursor 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, DbEnv.log_put and DbTxn.abort) 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 DbEnv.log_archive 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.)

See the db_archive manual page for more information on database archival procedures.

The DbEnv.log_archive method throws an exception that encapsulates a non-zero error value on failure.

# Bugs

In a threaded application (that is, one where the environment was created with the DB_THREAD flag specified), calling DbEnv.log_archive with the DB_ARCH_DATA flag will fail, returning EINVAL. To work around this problem, reopen the log explicitly without specifying DB_THREAD. This restriction is expected to be removed in a future version of Berkeley DB.

# Errors

The DbEnv.log_archive method may fail and throw an exception encapsulating a non-zero error for the following conditions:

EINVAL
  An invalid flag value or parameter was specified.

  The log was corrupted.

The DbEnv.log_archive method may fail and throw an exception for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the DbEnv.log_archive method may fail and throw a DbRunRecoveryException, in which case all subsequent Berkeley DB calls will fail in the same way.

# Class

DbEnv

# See Also

DbEnv.set_lg_bsize, DbEnv.set_lg_dir, DbEnv.set_lg_max, DbEnv.set_lg_regionmax, DbEnv.log_archive, DbEnv.log_compare, DbEnv.log_cursor, DbEnv.log_file, DbEnv.log_flush, DbEnv.log_put, DbEnv.log_register, DbEnv.log_stat, DbEnv.log_unregister, DbLogc.logc_close and DbLogc.logc_get.`

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