Note: These topics describe ABL transactions and related topics and is the primary programming documentation on transactions. One related topic, error handling, is more fully documented in ABL Error Handling. In particular, this guide describes structured error handling, which uses error objects and CATCH blocks to provide a more comprehensive and flexible error handling model. Structured error handling also provides the ability to pass error objects from an inner block to an outer block using the THROW syntax of an UNDO statement or the ON ERROR phrase.