#include <db.h>

int
DB_ENV->set_lg_bsize(DB_ENV *dbenv, 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 DB_ENV->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 DB_ENV->set_lg_bsize method configures a database environment, not only operations performed using the specified DB_ENV handle.

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

The DB_ENV->set_lg_bsize method returns a non-zero error value on failure and 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 DB_ENV->set_lg_bsize method may fail and return a non-zero error for the following conditions:

EINVAL

An invalid flag value or parameter was specified.

Called after DB_ENV->open was called.

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

The DB_ENV->set_lg_bsize method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions. If a catastrophic error has occurred, the DB_ENV->set_lg_bsize method may fail and return DB_RUNRECOVERY, in which case all subsequent Berkeley DB calls will fail in the same way.

Class

See Also