Berkeley DB: Db::close
Полезная информация


#include <db_cxx.h>

int Db::close(u_int32_t flags);


The Db::close method flushes any cached database information to disk, closes any open cursors, frees any allocated resources, and closes any underlying files. Since key/data pairs are cached in memory, failing to sync the file with the Db::close or Db::sync method may result in inconsistent or lost information.

The flags parameter must be set to 0 or the following value:

Do not flush cached information to disk.

The DB_NOSYNC flag is a dangerous option. It should only be set if the application is doing logging (with transactions) so that the database is recoverable after a system or application crash, or if the database is always generated from scratch after any system or application crash.

It is important to understand that flushing cached information to disk only minimizes the window of opportunity for corrupted data. While unlikely, it is possible for database corruption to happen if a system or application crash occurs while writing data to the database. To ensure that database corruption never occurs, applications must either: use transactions and logging with automatic recovery, use logging and application-specific recovery, or edit a copy of the database, and, once all applications using the database have successfully called Db::close, atomically replace the original database with the updated copy.

When multiple threads are using the Berkeley DB handle concurrently, only a single thread may call the Db::close method.

Once Db::close has been called, regardless of its return, the Berkeley DB handle may not be used again.

The Db::close method either returns errno or throws an exception that encapsulates an errno on failure, and 0 on success.


If a fatal error occurs in Berkeley DB, the Db::close method may fail and either return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY, at which point all subsequent database calls will also fail in the same way. Methods marked as returning errno will, by default, throw an exception that encapsulates the error information. The default error behavior can be changed, see

The Db::close method may fail and throw an exception for any of the errors specified for the following Berkeley DB and C library functions: Db::sync, DBcursor->c_close(3), dbc->c_am_destroy(3), dbm_close, dbp->am_close(3), fflush(3), fprintf(3), free(3), DbLog::db_unregister, DbMpool::close, DbMpoolFile::close, DbMpoolFile::sync, memset(3), vfprintf(3), and vsnprintf(3).



See Also

Db::close, Db::cursor, Db::del, Db::fd, Db::get, Db::get_byteswapped, Db::get_type, Db::join, Db::open, Db::put, Db::stat and Db::sync.