#include <db.h>

int
DB->sync(DB *db, u_int32_t flags);  

The DB->sync() method flushes any cached information to disk. This method operates on the database file level, so if the file contains multiple database handles then this method will flush to disk any information that is cached for any of those handles.

If the database is in memory only, the DB->sync() method has no effect and will always succeed.

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.

The DB->sync() method returns a non-zero error value on failure and 0 on success.