Berkeley DB: DbEnv::log_archive
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++

DbEnv::log_archive |

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    #include <db_cxx.h>

    int
    DbEnv::log_archive(char *(*listp)[], u_int32_t flags);

Description: DbEnv::log_archive

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, the memory location to which listp refers will be set to NULL.

Arrays of log filenames are stored in allocated memory. If application-specific allocation routines have been declared (see DbEnv::set_alloc for more information), they are used to allocate the memory; otherwise, the standard C library malloc(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.

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 db_archive for more information on database archival procedures.

The DbEnv::log_archive 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
flags

- The flags parameter must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values:
  DB_ARCH_ABS
  - All pathnames are returned as absolute pathnames, instead of relative to the database home directory.
  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.

    The DB_ARCH_DATA and DB_ARCH_LOG flags are mutually exclusive.

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

    The DB_ARCH_DATA and DB_ARCH_LOG flags are mutually exclusive.

  DB_ARCH_REMOVE
  - Remove log files that are no longer needed; no filenames are returned. Automatic log file removal is likely to make catastrophic recovery impossible.

    The DB_ARCH_REMOVE flag may not be specified with any other flag.

listp

- The listp 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 listp refers will be set to NULL.

Errors

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

EINVAL

- An invalid flag value or parameter was specified.

Class DbEnv, DbLogc, DbLsn
See Also Logging Subsystem and Related Methods`

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