Db::close()
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## Db::close()

    #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.

Although closing a database handle will close any open cursors, it is recommended that applications explicitly close all their Dbc handles before closing the database. The reason why is that when the cursor is explicitly closed, the memory allocated for it is reclaimed; however, this will not happen if you close a database while cursors are still opened.

The same rule, for the same reasons, hold true for DbTxn handles. Simply make sure you close all your transaction handles before closing your database handle.

Because key/data pairs are cached in memory, applications should make a point to always either close database handles or sync their data to disk (using the Db::sync() method) before exiting, to ensure that any data cached in main memory are reflected in the underlying file system.

When called on a database that is the primary database for a secondary index, the primary database should be closed only after all secondary indices referencing it have been closed.

When multiple threads are using the Db concurrently, only a single thread may call the `Db::close()` method.

The Db handle may not be accessed again after `Db::close()` is called, regardless of its return.

The `Db::close()` 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 be set to the following value:

- `DB_NOSYNC`

  Do not flush cached information to disk. This flag is a dangerous option. It should be set only 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. Although 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.

  Note that this flag only works when the database has been opened using an environment.

### Errors

The `Db::close()` method may fail and throw a DbException exception, 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

Db

### See Also

Database and Related Methods

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