I saw this table SysDataImpLogRef have over 1 mil records, and are dated 2011. Can I just delete the records in this table or AX have a job to delete it? Please advise, thank you.
It's really just a log, you can delete it without issues. When deleting data from SysDataImpLog table, you should also delete corresponding records from SysDataImpLog.
Standard AX2009 doesn't have any job for that, as far as I know.