The logging facility maintains in-memory log buffers. For every in-memory log buffer, there is a corresponding disk log file. Memory log buffers and disk log file blocks are the same length. The number of log buffers is configurable, set according to the performance requirements of the system. The logging system manages multiple asynchronous writes of log buffers to the log file.

The number of disk log file blocks corresponds to the size of the log file, and is specified when the log file is created. In a properly tuned system, most log file buffers are completely full of log records when they are written to the log file. However, as all log records associated with a transaction must be forced to the log file at certain times, principally at end transaction time, a small percentage of log file blocks may contain unused space. Server group commit logic is designed to minimize the frequency of log force operations and increase log file space use.