Consider Nike Inc. Let’s say Nike have 10000 Retail stores which produce a significant transactional data. If somebody high up in brass wants to see the sales details, that person will not look into the sales or invoice tables. Datamart provides that facility. It is a condensed version of a data warehouse displaying the important components of the trade. It is usually restricted to a particular department to cater to the needs of the top brass of that department.
A Nike Sales Head will be interested in a breakdown of sales in different product lines and demographics. Similarly, a Finance Head will be interested in the dollar numbers. Basically, a data mart can be defined as a repository of data from a larger source and designed to help a defined audience.
Operational Datamarts can cater to the intended audience in real time with SAP HANA. Either it is SAP Business Suite or non-SAP OLTP system, the raw data (transactional) is stored databases from which it is pulled into SAP HANA using SLT (SAP Landscape Transformation replication server) or SRS (SAP Replication Server). Any new data is moved into SAP HANA in similar fashion.
So, the question is what does HANA bring to the table? HANA works on the concept of the in-memory database. This means any data processing, even on large databases, is significantly quicker. When the data resides in HANA, the analytics aspect of data processing becomes way more time-efficient.