1. Oracle GoldenGate Classic Architecture Documentation
  2. Administer
  3. Data Management
  4. Creating a Data Definitions File

Creating a Data Definitions File

When replicating data from one table to another, an important consideration is whether the column structures (metadata) of the source and target tables are identical. Oracle GoldenGate looks up metadata for the following purposes:

Note:

This is only required when writing trails for Oracle GoldenGate 11.2 or earlier.

  • On the source, to supply complete information about captured operations to the Replicat process.

  • On the target, to determine the structures of the target tables, so that the replicated data is correctly mapped and converted (if needed) by Replicat.

When source and target table definitions are dissimilar, Oracle GoldenGate must perform a conversion from one format to the other. To perform conversions, both sets of definitions must be known to Oracle GoldenGate. Oracle GoldenGate can query the local database to get one set of definitions, but it must rely on a data-definitions file to get definitions from the remote database. The data-definitions file contains information about the metadata of the data that is being replicated.

To create a definitions file, you configure and run the DEFGEN utility and then transfer the definitions file to the target system. This file must be in place on the target system before you start the Oracle GoldenGate processes for the first time.