Some Q/A about SAP HANA
1. Why is HANA fast as compared to other databases?
Ans: HANA is an in-memory database and doesn’t rely on reading data from disk. The access to data is instantaneous. This is one of the primary reason why it is fast. Another reason is that it uses several compression logic to optimize storage of data. A database which may be around 10 GB in usual RDBMS may occupy 5 GB in HANA.
2. Isn’t HANA meant for only meant for SAP applications?
Ans: HANA is a just another database. It can be used with any application. Many organization are moving their business critical Non-SAP applications to HANA to make them fast.
3. Is it true that HANA is a column based? If so how is it different from Mongo DB?
Ans: HANA gives the flexibility to define tables as row or column store. Most column based DB like Mongo DB are more meant for OLAP / reporting. However, HANA is an available DB which can meet the needs for both OLAP and OLTP systems.
4. You mentioned HANA has both row and column store. Please explain when to use either.
Ans: The thumb rule is that you can define the row store when you have to do write operations on the table (transaction data). However, if a table is only for reading information, then it is best to define it as column store. Also, Column store can have high compression if the records are related to each other.
5. What steps would be involved in migrating an application to HANA.
Ans: The typical steps would be to change all the queries and make it HANA compatible. In this step, you may also want to remove all the select * and replace it with respective column names. Apart from this you may also want to export the data and import the same into HANA.
6. Is it possible to run an application on traditional database but run reporting on HANA?
Ans: Yes, it is possible to do so. However, in this case you may want to have data replication into HANA so that data changes in the application are also exported to HANA. Normal DB triggers can be used.