Transaction Log Truncation

   If log records were never deleted from the transaction log, it would eventually fill all the disk space that is available to the physical log files. Log truncation automatically frees space in the logical log for reuse by the transaction log.

Except when delayed for some reason, log truncation occurs automatically as follows:

• Under the simple recovery model, after a checkpoint.
• Under the full recovery model or bulk-logged recovery model, after a log backup, if a checkpoint has occurred since the previous backup.

For more information, see “Log truncation under the full and bulk-logged recovery models,” later in this topic.