About Extract Process : Oracle Goldengate 23ai

 The Extract process is configured to run against the source database, capturing data generated in the true source database located somewhere else. This process is the extraction or the data capture mechanism of Oracle Goldengate. 

You can configure an extract for the following use cases:

1. Initial Load

When you set up Oracle Goldengate for the initial load, the extract process captures the current, static set of data directly from the source objects. This configuration of extract process uses source tables as the source to capture data.

1. Online Extract (Change Synchronization)

When you set up Oracle Goldengate to keep the source data synchronized with another set of data, the extract process captures the DML and DL operations performed on the configured objects after the initial synchronization has taken place.

Extract process can run locally (upstream) on the same server as the database or on another server using the downstream integrated Extract (in case of Oracle database for reduced overhead.

The extract process stores these operations until it receives commit records or rollbacks for the transactions that contain them.

If it received a rollback, it discards the operations for that transaction. If it receives a commit, it persists the transaction to disk in series of files, called a trail, where it is queued for propagation to the target system.

All the operations in each trail file are written to the trail as a sequentially organized transaction unit and are in the order in which it was committed to the database ( Commit Sequence Order ). This design ensures both speed and data integrity.

This configuration of the Extract Process uses database recovery logs or transaction logs as the data source. Extract process ignores operations on objects that are not in the extract configuration.