Sets the size of the in-memory log buffer, in bytes.

For the DB, when the logging subsystem is configured for on-disk logging, the default size of the in-memory log buffer is approximately 32KB. For the BDB SQL interface, when the logging subsystem is configured for on-disk logging, the default size of the in-memory log buffer is approximately 64KB. Log information is stored in-memory until the storage space fills up or a 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.

When the logging subsystem is configured for in-memory logging, the default size of the in-memory log buffer is 1MB. Log information is stored in-memory until the storage space fills up or transaction abort or commit frees up the memory for new transactions. In the presence of long-running transactions or transactions producing large amounts of data, the buffer size must be sufficient to hold all log information that can accumulate during the longest running transaction. 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.

The syntax of this parameter in the DB_CONFIG file is a single line with the string set_lg_bsize, one or more whitespace characters, and the log buffer size in bytes.

If the database environment already exists when this parameter is changed, it is ignored. To change this value after the environment has been created, re-create your environment.

For more information, see DbEnv::set_lg_bsize().