#include <db_cxx.h> int DbEnv::log_set_config(u_int32_t flags, int onoff);
        The DbEnv::log_set_config() method
        configures the Berkeley DB logging subsystem.
    
        The DbEnv::log_set_config() method
        configures a database environment, not only operations performed
        using the specified DbEnv  handle.
    
        The DbEnv::log_set_config() method may be
        called at any time during the life of the application.
    
        The DbEnv::log_set_config() 
            
            
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.
            
        
    
The flags parameter must be set by bitwise inclusively OR'ing together one or more of the following values:
If set, Berkeley DB will automatically remove log files that are no longer needed.
Automatic log file removal is likely to make catastrophic recovery impossible.
Replication Manager applications operate in a group-aware manner for log file removal, and automatic log file removal simplifies the application.
Replication Base API applications will rarely want to configure automatic log file removal as it increases the likelihood a master will be unable to satisfy a client's request for a recent log record.
                        Calling
                        DbEnv::log_set_config()
                        with the DB_LOG_AUTO_REMOVE flag
                        affects the database environment, including all
                        threads of control accessing the database
                        environment.
                    
                        The DB_LOG_AUTO_REMOVE flag may
                        be used to configure Berkeley DB at any time during
                        the life of the application.
                    
Enables full logging of BLOB data. Only use this flag if using replication or running a hot backup; otherwise, it will impose a performance penalty on BLOB operations.
This flag is off by default, unless Replication is enabled for the environment. In that case, it is on by default.
                        The DB_LOG_BLOB flag may be
                        used to configure Berkeley DB at any time during
                        the life of the application.
                    
Turn off system buffering of Berkeley DB log files to avoid double caching.
                        Calling
                        DbEnv::log_set_config()
                        with the DB_LOG_DIRECT flag only affects the
                        specified DbEnv
                        handle (and any other Berkeley DB handles opened
                        within the scope of that handle). For consistent
                        behavior across the environment, all 
                        DbEnv  handles
                        opened in the environment must either set the
                        DB_LOG_DIRECT flag or the flag should be specified
                        in the DB_CONFIG configuration file.
                    
                        The DB_LOG_DIRECT flag may be
                        used to configure Berkeley DB at any time during
                        the life of the application.
                    
Configure Berkeley DB to flush log writes to the backing disk before returning from the write system call, rather than flushing log writes explicitly in a separate system call, as necessary. This is only available on some systems (for example, systems supporting the IEEE/ANSI Std 1003.1 (POSIX) standard O_DSYNC flag, or systems supporting the Windows FILE_FLAG_WRITE_THROUGH flag). This flag may result in inaccurate file modification times and other file-level information for Berkeley DB log files. This flag may offer a performance increase on some systems and a performance decrease on others.
                         Calling
                         DbEnv::log_set_config()
                         with the DB_LOG_DSYNC flag only affects the
                         specified DbEnv
                         handle (and any other Berkeley DB handles opened
                         within the scope of that handle). For consistent
                         behavior across the environment, all 
                         DbEnv  handles
                         opened in the environment must either set the
                         DB_LOG_DSYNC flag or the flag should be specified
                         in the DB_CONFIG configuration file.
                     
                        The DB_LOG_DSYNC flag may be
                        used to configure Berkeley DB at any time during
                        the life of the application.
                     
If set, maintain transaction logs in memory rather than on disk. This means that transactions exhibit the ACI (atomicity, consistency, and isolation) properties, but not D (durability); that is, database integrity will be maintained, but if the application or system fails, integrity will not persist. All database files must be verified and/or restored from a replication group master or archival backup after application or system failure.
                        When in-memory logs are configured and no more log
                        buffer space is available, Berkeley DB methods may
                        return an additional error value,
                        DB_LOG_BUFFER_FULL.  When
                        choosing log buffer and file sizes for in-memory
                        logs, applications should ensure the in-memory log
                        buffer size is large enough that no transaction
                        will ever span the entire buffer, and avoid a state
                        where the in-memory buffer is full and no space can
                        be freed because a transaction that started in the
                        first log "file" is still active.
                    
                        Calling
                        DbEnv::log_set_config()
                        with the DB_LOG_IN_MEMORY flag
                        affects the database environment, including all
                        threads of control accessing the database
                        environment.
                    
                        The DB_LOG_IN_MEMORY flag may be
                        used to configure Berkeley DB only before the 
                        DbEnv::open()
                        method is called.
                    
                        DB_LOG_ZERO
                    
If set, zero all pages of a log file when that log file is created. This has shown to provide greater transaction throughput in some environments. The log file will be zeroed by the thread which needs to re-create the new log file. Other threads may not write to the log file while this is happening.
                        Calling
                        DbEnv::log_set_config()
                        with the DB_LOG_ZERO flag
                        affects only the current environment handle.
                    
                        The DB_LOG_ZERO flag may be used
                        to configure Berkeley DB at any time.
                    
             The DbEnv::log_set_config() 
            
            
                method may fail and throw a DbException 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors: