The extraction daemon, whether primary or standby, starts when an instance is started by specifying userlog for shared_preload_libraries in postgresql.conf. The extraction control file must be initialized before starting. Refer to "Chapter 2 Setup" for detailed instructions.

The extraction daemon reads the user and transaction completion logs from the archive file location specified by userlog.archive_directory in postgresql.conf.

The read userlogs are organized for each transaction and stored in memory, and when the transaction completion log is read, all userlogs for that transaction are output to an extract file in the directory specified in userlog.directory in postgresql.conf.