PERSIST_WAL

The SQLITE_FCNTL_PERSIST_WAL opcode is used to set or query the persistent Write Ahead Log setting. By default, the auxiliary write ahead log (WAL file) and shared memory files used for transaction control are automatically deleted when the latest connection to the database closes. Setting persistent WAL mode causes those files to persist after close. Persisting the files is useful when other processes that do not have write permission on the directory containing the database file want to read the database file, as the WAL and shared memory files must exist in order for the database to be readable. The fourth parameter to sqlite3_file_control() for this opcode should be a pointer to an integer. That integer is 0 to disable persistent WAL mode or 1 to enable persistent WAL mode. If the integer is -1, then it is overwritten with the current WAL persistence setting.