Hello Chenzhian,
Just as S Sriram mentioned, you can use R3load to do the migration.
And also another opinion, you can use backup/restore method to do system copy from SLES to RHEL for HANA (same endian, you can update to the latest HANA version. Maybe you need confirmation from SAP side, I'm not sure about that if it is support from SLES to RHEL) .
Regards,
Ning Tong