Basic Questions and Answers related to SAP-HANA and Views - 1

1. Explain Parallel Processing in SAP HANA?

Using the columnar data storage approach, the workload in SAP HANA is divided vertically. The columnar approach allows linear searching and aggregation of data rather than two-dimensional data structure. If more than one column is to be processed, each task is assigned to diverse processor. Operations on one column are then collimated by column divisions processed by different processors.

 2. List advantages of using SAP HANA database

With the HANA technology, you can create gen-next applications giving effective and efficient results in the digital economy.

By using singe data-in memory, SAP HANA supports smooth transaction process and fault-tolerant analytics

Easy and simple operations using an open-source, unified platform in the cloud

High-level Data Integration to access massive amounts of data

Advanced tools for in-depth analysis of present, past and the future

3. List the merits and demerits of using row-based tables.

Merits:

No data approach can be faster than row-based if you want to analyze process and retrieve one record at one time.

Row-based tables are useful when there is specific demand of accessing complete record.

It is preferred when the table consists of less number of rows.

This data storage and processing approach is easier and effective without any aggregations and fast searching.

Demerits:

The data retrieval and processing operations involve the complete row, even though all the information is not useful.

4. List advantages of column-based tables

Allows smoother parallel processing of data as the data in columns is stored vertically. Thus, to access data from multiple columns, every operation can be allocated to a separate processor core.

Only specific columns need to be approached for Select query and any column can be used for indexing.

Efficient operations since most columns hold unique values and thus, high compression rate.

5. Mention what is modeling studio?

Modeling studio in HANA performs multiple tasks like

Declares which tables are stored in HANA, first part is to get the meta-data and then schedule data replication jobs

Manage Data Services to enter the data from SAP Business Warehouse and other systems

Manage ERP instances connection, the current release does not support connecting to several ERP instances

Use data services for the modeling

Do modeling in HANA itself

Essential licenses for SAP BO data services

6. Mention what is the role of the persistence layer in SAP HANA?

SAP HANA has an in-memory computing engine and access the data straightaway without any backup. To avoid the risk of losing data in case of hardware failure or power cutoff, persistence layer comes as a savior and stores all the data in the hard drive which is not volatile.

7. What is Text Join?
Text Join is used in order to get language-specific data. 
You have a product table that contains product IDs without descriptions and you have a text table for products that contains language-specific descriptions for each product.
You can create a text join between the two tables to get the language-specific details.
In a text join, the right table should be the text table and it is mandatory to specify the Language Column. 

8. What is time attribute view?

A. Time attribute view is used to analyze data based on the time characteristics like year, quarter, month and day.

It is based on time period.

Two things we need to have when we are creating a time dimension

1. Calendar type

2. Granularity

In time attribute view we have two types of calendars

1. Gregorian calendar

2. Fiscal calendar

1. GREGORIAN CALENDER:

·         A Gregorian calendar is the jan-dec calendar that goes by what we a calendar year.

2. FISCAL CALENDER:

·         A fiscal calendar is the one that defines a fiscal year.

·         Depending on the country, this can be jan-dec,apr_mar,jul-jun etc

In general, the time attribute view would normally be created based on time dimension table (_SYS_BI.M_TIME_DIMENSION)

Fiscal calendar table (_SYS_BI.M_FISCAL_CALENDAR)

9. Can you give definition of all 3 schemas again?

​A._SYS_BI: This schema stores all the Meta data of created column views. It contains tables for created variables, Time Data (FISCAL, Gregorian), schema mapping and content
 mapping tables.

_SYS_REPO: This schema stores all the design time models under content.
_SYS_BIC: This schema stores for all the generated run time objects. So basically when we activate the Information models/views they are created as a column views in this schema.​

10. What is attribute view?

A.    Attribute views are known as reusable dimensions used to join master data

A DIMENSION is a perspective in which you want to analyze data.

Attribute views execute in an engine called JOIN engine.

JOIN engine is optimized for processing complex joins.

11. What SPARS means?

A. Whenever we define join type as Text Join then we need to specify language column as SPARS to give the description based on language.

12. Is text always used to specify the languages?

Yes, Text Join is used in order to get language-specific data. 

You have a product table that contains product IDs without descriptions and you have a text table for products that contains language-specific descriptions for each product.

You can create a text join between the two tables to get the language-specific details.

In a text join, the right table should be the text table and it is mandatory to specify the Language Column.

Whenever we define join type as Text Join then we need to specify language column as SPARS to give the description based on language.

13. What is cardinality? Why it’s required in Data foundation?

A. Cardinality is a property of a join that describes how many rows in one table match rows in another table.

It’s not mandatory to define cardinalities between two tables but is a Best practice to do so. If you set the cardinalities, in the integrity check, BO tool will allow showing you join divergence or possible Traps in your structure and also it helps for any third person to see and understand the relationship.

If you don't set it, it is not going to impact in anything as the SQL generated is not dependent on cardinalities which are set in Universe structure.