#include <db_cxx.h>

int
DbEnv::set_lg_bsize(u_int32_t lg_bsize);

Description

Set the size of the in-memory log buffer, in bytes. By default, or if the value is set to 0, a size of 32K is used. The size of the log file (see DbEnv::set_lg_max) must be at least four times the size of the the in-memory log buffer.

Log information is stored in-memory until the storage space fills up or transaction commit forces the information to be flushed to stable storage. In the presence of long-running transactions or transactions producing large amounts of data, larger buffer sizes can increase throughput.

The DbEnv::set_lg_bsize method configures a database environment, not only operations performed using the specified DbEnv handle.

The DbEnv::set_lg_bsize interface may not be called after the DbEnv::open interface is called. If the database environment already exists when DbEnv::open is called, the information specified to DbEnv::set_lg_bsize will be ignored.

The DbEnv::set_lg_bsize 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 database environment's log buffer size may also be set using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "set_lg_bsize", one or more whitespace characters, and the size in bytes. Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.

Errors

The DbEnv::set_lg_bsize method may fail and throw an exception or return a non-zero error for the following conditions:

EINVAL

An invalid flag value or parameter was specified.

Called after DbEnv::open was called.

The size of the log file is less than four times the size of the in-memory log buffer.

The DbEnv::set_lg_bsize method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods. If a catastrophic error has occurred, the DbEnv::set_lg_bsize method may fail and either return DB_RUNRECOVERY or throw a DbRunRecoveryException, in which case all subsequent Berkeley DB calls will fail in the same way.

Class

See Also