Hi Syed
YES, it is possible to do migration ECC6 with DB oracle 11G & OS windows 2008 to SAP HANA ,But after upgrade from EHP5 to EHP6
With SAP enhancement package 6 for SAP ERP 6.0, version for SAP HANA, SAP is enabling the existing functions of SAP ERP for SAP HANA to utilize the in-memory technology and enable better performing business applications. Thereby, business application can manage also large data volumes significantly faster. SAP HANA comprises the required hardware as well as the SAP HANA appliance software (SAP HANA database and data replication tools, for example).
Please note that the specific observed performance is depending on configuration, data volumes and data constellation.
SAP enhancement package 6 for SAP ERP 6.0, version for SAP HANA is technically very similar to an enhancement package, however it is not part of the release sequence of EHPs of SAP ERP. It is an optional intermediate step for early adopters on their way to SAP HANA.
Please consider that some industries solutions, add-ons or functions will not be supported with SAP enhancement package 6 for SAP ERP 6.0, version for SAP HANA. This release is a product outside the release sequence of SAP ERP.
also, refer the link- Migrate