Database triggers are specialized stored programs. They are not called directly but are triggered by events in the database. They run between the time you issue a command and the time you perform the database management system action. This time interval is the transaction lifecycle. You can read more about the transaction lifecycle in the “Data Transactions” section of Appendix A. Appendix A also discusses ACID-compliant transactions and the two-phase commit (2PC) processes, in the section “Data Transactions.” Together, they support the Oracle Database implementation of MVCC.