More about trail files
Trail files are used by Extract and Replicat processes; their primary role is for data persistence. You could argue that writing files to what could be deemed as a staging area is wasteful and suboptimal. Having said that, GoldenGate writes only the committed transactions to trail files in large blocks minimizing I/O. Furthermore, the architecture provides a guaranteed no data loss solution that is not to be underestimated.
The trail
By default, trail files are in the canonical format being unstructured, but with a header record. They are stored in the ./dirdat subdirectory under the GoldenGate Home. Each record contains the changed data and is of a variable record length. A trail can contain numerous trail files, each having a two-character prefix with a six-digit sequence number suffix.
An Extract process can write data to many trails. A Replicat can process data from only one trail. In classic mode, it is possible to configure multiple Replicat processes to handle...