1. A computer-implemented method for reversing changes to a structure of a relational database, the computer-implemented method comprising executing instructions in a computer system to perform the operations of: receiving data defining a database definition language (DDL) transaction comprising DDL operations for modifying a structure of the relational database; storing data that includes instructions for the DDL operations for use in reversing changes made to the structure of the relational database by the DDL operations and data that describes a state of the relational database prior to the performance of the DDL operations; performing the DDL operations to modify the structure of the relational database; determining that the performance of any of the DDL operations has failed; and in response to determining that the performance of any of the DDL operations has failed, utilizing the stored data to reverse the changes made to the structure of the relational database by the DDL operations.