Yes, the SAP HANA Database is a full-fledged, in-memory, relational database which is optimized for transactional (OLTP) and analytical (OLAP) processing.

It is even more than just a database: SAP HANA is a platform which combines database, data processing, and application platform capabilities in-memory. The platform provides libraries for predictive, planning, text processing, spatial, and business analytics.
 

2. Is SAP HANA a replacement for the Database in SAP ERP?

SAP HANA is not a “replacement” but more an alternative which offers a higher performance and advanced capabilities such as integrated data mining and predictive analysis for gaining new business insights.

SAP HANA is supported as primary database starting with SAP NetWeaver AS ABAP 7.4 which is the foundation of SAP Business Suite (SAP ECC Core 6.0). Other classical databases such as Oracle, DB2 and SQL are still supported.
 

3. Presently I use Oracle in the back end for database in my SAP ERP ECC 6.0 . So can it be replaced with SAP HANA.

Starting with SAP Business Suite Innovations 2013 /SAP EHP7 for SAP ERP 6.0 (with SAP NetWeaver 7.4 as foundation) customers have the possibility to migrate their existing primary database to SAP HANA. But of course, they can also keep their existing ones (e.g. Oracle in your case). A SAP EhP6 for SAP ERP 6.0 version for SAP HANA exists.
 

4. In future, will SAP HANA replace the Oracle in SAP ERP ECC .

As already mentioned above, customers have the choice to decide on which database their want to run their businesses. SAP HANA is an option among others.  But in order to benefit from the advanced and innovative capabilities offered by SAP HANA, a migration of existing classical database to the SAP HANA Database should be taken into consideration.
 

5.Should a person have ABAP knowledge to learn SAP HANA. Can you please clarify my doubts?

No, ABAP knowledge is not a requirement for learning SAP HANA.

SAP HANA is a separate platform (database and more). It supports standard SQL, but also other languages such as SQLScript, which is a collection of SAP HANA specific extensions to SQL.

There are two major development scenarios around SAP HANA:

i) Building native SAP HANA applications based on SAP HANA Extended Application Services (SAP HANA XS) - (SQL, SQLScript, javaScript,...)

ii) Building ABAP for SAP HANA applications - meaning applications which are built out of ABAP and SAP HANA development entities.
With SAP NetWeaver 7.4, the ABAP language has been optimized for SAP HANA and allows the native ABAP consumption of SAP HANA entities (views and procedures).

A possible option in this case is having matter experts: ABAP experts and HANA experts working on a project.

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