Read/write concurrency can now be enabled in the SQL API by using
        PRAGMA multiversion=on before accessing any
        tables in the database.  After multiversion has been enabled, it
        can be temporarily disabled using the 
        PRAGMA transaction_snapshots=on/off.
    
For more details on pragmas concerning Transaction Snapshots read Using Multiversion Concurrency Control in the Berkeley DB Getting Started with the SQL APIs guide.
PRAGMA multiversion=ON|OFF;
            PRAGMA snapshot_isolation=ON|OFF