An activity that includes generating and testing a sequence of statements, expressed in Data Definition Language (DDL), which delete, create or alter database objects. The DDL sequence of statements is usually generated by request to a data modeling tool from a Physical Data Model (PDM). It can also be generated from the database itself for the purposes of Reverse Engineering or copying the existing structure into another database. The Data Base Management System (DBMS) will execute the submitted DDL sequence to actualize the changes to the database. After the DDL sequence is generated and before it is executed, it can be manually modified, e.g. by the Data Base Administrators to add or modify space utilization and performance parameters. If a direct connection can be established between the data modeling tool and the database, then the DDL sequence is executed as it is generated.
This is an activity that pre-exists TDM. TDM suggests the enforcement of good practices surrounding database structure changes. A reverse engineered PDM should be created from the production database just after official structure change implementations and on a scheduled basis between implementations to refresh the PDM of record with non-structural changes and to insure no unapproved structural changes have occurred.