参考官方文档如下:

https://docs.oracle.com/en/middleware/goldengate/core/18.1/hetergeneous-db/preparing-and-configuring-system-oracle-goldengate.html#GUID-A2FDBF55-48DA-4C7F-9F1F-152275206D71

Positioning Extract to a Specific Start Point

You can position the ADD EXTRACT and ALTER EXTRACT commands to a specific start point in the transaction logs with the following command.

{ADD | ALTER EXTRACT} group, VAM, LOGNUM log_num, LOGPOS log_pos                    

group is the name of the Oracle GoldenGate Extract group for which the start position is required.

log_num is the log file number. For example, if the required log file name is test.000034, this value is 34. Extract will search for this log file.

log_pos is an event offset value within the log file that identifies a specific transaction record. Event offset values are stored in the header section of a log record. To position at the beginning of a binlog file, set the log_pos as 4. The log_pos 0 or 1 are not valid offsets to start reading and processing.

In MySQL logs, an event offset value can be unique only within a given binary file. The combination of the position value and a log number will uniquely identify a transaction record and cannot exceed a length of 37. Transactional records available after this position within the specified log will be captured by Extract. In addition, you can position an Extract using a timestamp.