2.2. Write-Ahead Log (WAL) Files A write-ahead log or WAL file is used in place of a rollback journal when SQLite is operating in WAL mode. As with the rollback journal, the purpose of the WAL file is to implement atomic commit and rollback ... 

SQLITE_FCNTL_LOCKSTATE, SQLITE_FCNTL_GET_LOCKPROXYFILE, SQLITE_FCNTL_SET_LOCKPROXYFILE, SQLITE_FCNTL_LAST_ERRNO, SQLITE_FCNTL_SIZE_HINT, SQLITE_FCNTL_CHUNK_SIZE ... 

 ... 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. The SQLITE_FCNTL_POWERSAFE_OVERWRITE opcode is used to set or query ... 

4.4. WAL Reset After a complete checkpoint, if no other connections are in transactions that use the WAL, then subsequent write transactions can overwrite the WAL file from the beginning. This is called "resetting the WAL". At the start of the first new ... 

 ... Similarly, "app.db-wal" will become "app.wal" and "app.db-shm" becomes "app.shm". Note that it is very important that the database filename have some kind of extension. If there is no extension, then SQLite creates auxiliary filenames ... 

 ... Since version 3.7.0 (2010-07-21), SQLite also supports "WAL mode". In WAL mode, changes are not written to the original database file. Instead, changes go into a separate "write-ahead log" or "WAL" file. Later, after the ... 

sqlite3_deserialize()

 ... The deserialized database should not be in WAL mode. If the database is in WAL mode, then any attempt to use the database file will result in an SQLITE_CANTOPEN error. The application can set the file format version numbers (bytes ... 

 ... Transactions involving multiple attached databases are atomic, assuming that the main database is not ":memory:" and the journal_mode is not WAL. If the main database is ":memory:" or if the journal_mode is WAL, then transactions continue to be atomic within ... 

sqlite3_database_file_object()

If X is the name of a rollback or WAL-mode journal file that is passed into the xOpen method of sqlite3_vfs, then sqlite3_database_file_object(X) returns a pointer to the sqlite3_file object that represents the main database file. This routine ... 

8.2. Corruption following switches between rollback and WAL modes Repeatedly switching an SQLite database in and out of WAL mode and running the VACUUM command in between switches, in one process or thread, can cause another process or thread that has the database file open to miss the fact ... 

PRAGMA synchronous  ... In WAL mode when synchronous is NORMAL (1), the WAL file is synchronized before each checkpoint and the database file is synchronized after each completed checkpoint and the WAL file header is synchronized when a WAL file begins to be ...