The Db::close method flushes any cached database information to disk,
closes any open cursors, frees any allocated resources, and closes any
underlying files. Because 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 value must be set to 0 or by bitwise inclusively OR'ing together one or
more of the following values:
- Do not flush cached information to disk. The DB_NOSYNC 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
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.
The Db::close method may fail and throw an exception or return a non-zero error for the following conditions:
- An invalid flag value or parameter was specified.
The Db::close method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
If a catastrophic error has occurred, the Db::close method may fail and
either return DB_RUNRECOVERY or throw a
in which case all subsequent Berkeley DB calls will fail in the same way.
Databases and Related Methods
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