As explained in the eXtremeDB Transaction Logging User's Guide, Transaction Logging (TL) provides for recovery of an eXtremeDB in-memory database in the event of failure, “Data Relay” to external systems and for creating a persistent queue of events. The TL Introduction gives an overview of TL and the TL Applications page explains how TL APIs are incorporated into applications. The TL_HA page describes how to incorporate TL in eXtremeDB High Availability and/or eXtremeDB Cluster applications.