The Db.sync method flushes any cached information to disk.
If the database is in memory only, the Db.sync method has no effect and
will always succeed.
The flags parameter is currently unused, and must be set to 0.
See Db.close for a discussion of Berkeley DB and cached data.
The Db.sync method throws an exception that encapsulates a non-zero error value on
failure, and returns Db.DB_INCOMPLETE if the underlying database still has
dirty pages in the cache. (The only reason to return
Db.DB_INCOMPLETE is if another thread of control was writing pages
in the underlying database file at the same time as the
Db.sync method was being called. For this reason, a return of
Db.DB_INCOMPLETE can normally be ignored, or, in cases where it is
a possible return value, there may be no reason to call
Db.sync.)
Errors
The Db.sync 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 Db.sync 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 Db.sync method may fail and throw
a DbRunRecoveryException, in which case all subsequent Berkeley DB calls
will fail in the same way.