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Qs. What is SAP HANA?

SAP HANA is an in-memory database.

o It is a combination of hardware and software made to process

massive real time data using In-Memory computing.

o It combines row-based, column-based database technology.

o Data now resides in main-memory (RAM) and no longer on a hard

disk.

o It’s best suited for performing real-time analytics, and developing and

deploying real-time applications.

An in-memory database means all the data is stored in the memory (RAM).

This is no time wasted in loading the data from hard-disk to RAM or while

processing keeping some data in RAM and temporary some data on disk.

Everything is in-memory all the time, which gives the CPUs quick access to

data for processing.

SAP HANA is equipped with multiengine query processing environment which

supports relational as well as graphical and text data within same system. It

provides features that support significant processing speed, handle huge data


sizes and text mining capabilities.

Qs. So is SAP making/selling the software or the

hardware?

SAP has partnered with leading hardware vendors (HP, Fujitsu, IBM, Dell etc)

to sell SAP certified hardware for HANA.

SAP is selling licenses and related services for the SAP HANA product which

includes the SAP HANA database, SAP HANA Studio and other software to

load data in the database.

Qs. What is the language SAP HANA is developed in?

The SAP HANA database is developed in C++.

Qs. What is the operating system supported by HANA?


Currently SUSE Linux Enterprise Server x86-64 (SLES) 11 SP1 is the

Operating System supported by SAP HANA.

Qs. Can I just increase the memory of my traditional

Oracle database to 2TB and get similar performance?

NO.

You might have performance gains due to more memory available for your

current Oracle/Microsoft/Teradata database but HANA is not just a database

with bigger RAM.

It is a combination of a lot of hardware and software technologies. The way

data is stored and processed by the In-Memory Computing Engine (IMCE) is

the true differentiator. Having that data available in RAM is just the icing on

the cake.

Qs. What are the row-based and column based

approach?

Row based tables:

o It is the traditional Relational Database approach

o It store a table in a sequence of rows

Column based tables:


o It store a table in a sequence of columns i.e. the entries of a column

is stored in contiguous memory locations.

o SAP HANA is particularly optimized for column-order storage.

SAP HANA supports both row-based and column-based approach.

Following figure explains the difference between the two storage mechanism.


Qs. What are the advantages and disadvantages of row-

based tables?

Row based tables have advantages in the following circumstances:

o The application needs to only process a single record at one time

(many selects and/or updates of single records).

o The application typically needs to access a complete record (or row).

o Neither aggregations nor fast searching are required.

o The table has a small number of rows (e. g. configuration tables,

system tables).

Row based tables have dis-advantages in the following circumstances:

o In case of analytic applications where aggregation are used and fast

search and processing is required. In row based tables all data in a

row has to be read even though the requirement may be to access

data from a few columns.

o

Qs. What are the advantages of column-based tables?

Advantages:

o Faster Data Access:


Only affected columns have to be read during the selection process of a

query. Any of the columns can serve as an index.

o Better Compression:

Columnar data storage allows highly efficient compression because the

majority of the columns contain only few distinct values (compared to number

of rows).

o Better parallel Processing

In a column store, data is already vertically partitioned. This means that

operations on different columns can easily be processed in parallel. If multiple

columns need to be searched or aggregated, each of these operations can be

assigned to a different processor core

Qs. In HANA which type of tables should be preferred -

Row-based or Column-based?

SQL queries involving aggregation functions take a lot of time on huge

amounts of data because every single row is touched to collect the data for

the query response.

In columnar tables, this information is stored physically next to each other,

significantly increasing the speed of certain data queries. Data is also

compressed, enabling shorter loading times.

Conclusion:

To enable fast on-the-fly aggregations, ad-hoc reporting, and to benefit from

compression mechanisms it is recommended that transaction data is stored in


a column-based table.

The SAP HANA data-base allows joining row-based tables with column-based

tables. However, it is more efficient to join tables that are located in the same

row or column store. For example, master data that is frequently joined with

transaction data should also be stored in column-based tables.

Few more important points about column table:

1. HANA modeling views are only possible for column tables. Row based

tables cannot be used in modeling views.

2. For that reason Replication Server creates SAP HANA tables in column

store by default.

3. Data Services also creates target tables in column store as default for SAP

HANA database

4. The SQL command to create column table: “CREATE COLUMN TABLE

Table_Name..”.

5. The data storage type of a table can be modified from Row to Column

storage with the SQL command “ALTER TABLE Table_Name COLUMN“.


Qs. Why materialized aggregates are not required in

HANA?

Since the SAP HANA database resides entirely in-memory all the time,

additional complex calculations, functions and data-intensive operations can

happen on the data directly in the database. Hence materialized aggregations

are not required.

It also provides benefits like

o Simplified data model

o Simplified application logic

o Higher level of concurrency

Qs. How does SAP HANA support Massively Parallel

Processing?

With availability of Multi-Core CPUs, higher CPU execution speeds can be

achieved.

Also HANA Column-based storage makes it easy to execute operations in

parallel using multiple processor cores.

In a column store data is already vertically partitioned. This means that


operations on different columns can easily be processed in parallel. If multiple

columns need to be searched or aggregated, each of these operations can be

assigned to a different processor core.

In addition operations on one column can be parallelized by partitioning the

column into multiple sections that can be processed by different processor

cores. With the SAP HANA database, queries can be executed rapidly and in

parallel.

Qs. Why SAP HANA is fast?


Qs. Describe SAP HANA Database Architecture in

brief.

The SAP HANA database is developed in C++ and runs on SUSE Linux

Enterpise Server. SAP HANA database consists of multiple servers and the

most important component is the Index Server. SAP HANA database consists

of Index Server, Name Server, Statistics Server, Preprocessor Server and XS

Engine.


Index Server:

o Index server is the main SAP HANA database component

o It contains the actual data stores and the engines for processing the

data.

o The index server processes incoming SQL or MDX statements in the

context of authenticated sessions and transactions.

Persistence Layer:

The database persistence layer is responsible for durability and atomicity of

transactions. It ensures that the database can be restored to the most recent

committed state after a restart and that transactions are either completely

executed or completely undone.

Preprocessor Server:

The index server uses the preprocessor server for analyzing text data and

extracting the information on which the text search capabilities are based.

Name Server:

The name server owns the information about the topology of SAP HANA

system. In a distributed system, the name server knows where the

components are running and which data is located on which server.


Statistic Server:

The statistics server collects information about status, performance and

resource consumption from the other servers in the system.. The statistics

server also provides a history of measurement data for further analysis.

Session and Transaction Manager:

The Transaction manager coordinates database transactions, and keeps track

of running and closed transactions. When a transaction is committed or rolled

back, the transaction manager informs the involved storage engines about this

event so they can execute necessary actions.

XS Engine:

XS Engine is an optional component. Using XS Engine clients can connect to

SAP HANA database to fetch data via HTTP.

Qs.What is ad hoc analysis?

In traditional data warehouses, such as SAP BW, a lot of pre-aggregation is

done for quick results. That is the administrator (IT department) decides which

information might be needed for analysis and prepares the result for the end

users. This results in fast performance but the end user does not have

flexibility.


The performance reduces dramatically if the user wants to do analysis on

some data that is not already pre-aggregated. With SAP HANA and its speedy

engine, no pre-aggregation is required. The user can perform any kind of

operations in their reports and does not have to wait hours to get the data

ready for analysis.

Qs. What are the different types of replication techniques?

There are 3 types of replication techniques:

1. SAP Landscape Transformation (SLT)

2. SAP Business Objects Data Services (BODS)

3. SAP HANA Direct Extractor Connection (DXC)

Note: There is one more replication technique called Sybase replication. It was

part of initial offering for HANA replication, but not positioned / supported

anymore due to licensing issues and complexity and mostly because SLT

provides the same features.

Qs. What is SLT?

The SAP Landscape Transformation (LT) Replication Server is the SAP

technology that allows us to load and replicate data in real-time from SAP source

systems and non-SAP source systems to an SAP HANA environment.

The SAP LT Replication Server uses a trigger-based replication approach to


pass data from the source system to the target system.

Qs. What is the advantage of SLT replication?

Advantages:

1. SAP LT uses trigger based approach. Trigger-based approach has no

measureable performance impact in source system.

2. It provides transformation and filtering capability.

3. It allows real-time (and scheduled) data replication, replicating only relevant

data into HANA from SAP and non-SAP source systems.

4. It is fully integrated with HANA Studio.

5. Replication from multiple source systems to one HANA system is allowed,

also from one source system to multiple HANA systems.

Qs. Is it possible to use a replication for multiple sources

and target SAP HANA systems?


Yes, the SAP LT Replication Server supports both 1:N replication and and N:1

replication.

o • Multiple source system can be connected to one SAP HANA system.

o • One source system can be connected to multiple SAP HANA systems.

Limited to 1:4 only.

Qs. Is there any pre-requisite before creating the

configuration and replication?

For SAP source systems:

1. DMIS add-on must be installed in SLT replication server.


2. An RFC connection between the SAP source system and the SAP LT

Replication Server has to be established.

3. User for RFC connection must have the role IUUC_REPL_REMOTE

assigned.

4. Do not use a DDIC user for RFC connection.

For non-SAP source systems:

1. DMIS add-on is not required.

2. A database user has to be created with appropriate authorizations in

advance and establish the database connection by using transaction DBCO

in the SAP LT Replication Server.

3. Ensure the database-specific library components for the SAP 7.20 REL or

EXT kernel are installed in the SAP LT Replication Server.

Qs. What is Configuration and Monitoring Dashboard?

It is an application that runs on SLT replication server to specify configuration

information (such as source system, target system, and relevant connections) so

that data can be replicated.

It can also use it to monitor the replication status (transaction LTR).

Status Yellow: It may occur due to triggers which are not yet created

successfully.


Status Red: It may occur if master job is aborted (manually in transaction SM37).

Qs. What is advanced replication settings (transaction

IUUC_REPL_CONT)?

The Advanced Settings (transaction IUUC_REPL_CONT) allows you to define

and change various table settings for a configuration such as:

o • Partitioning and structure changes for target tables in HANA

o • Table-specific transformation and filter rules

o • Adjusting the number of jobs (and reading type) to accelerate the

load/replication process

Qs. What is Latency?

It is the length of time to replicate data (a table entry) from the source system to

the target system.

Qs. What is logging table?

A table in the source system that records any changes to a table that is being

replicated. This ensures that SLT replication server can replicate these changes

to the target system.

Qs. What are Transformation rules?


A rule specified in the Advanced Replication settings transaction for source

tables such that data is transformed during the replication process. Example you

can specify rule to

o • Convert fields

o • Fill empty fields

o • Skip records

Qs. What happens when you set-up a new configuration?

When a new configuration in the SAP LT Replication Server is created, the

database connection is automatically created along with a schema GUID and

Mass transfer id (MT_ID).

A schema GUID ensures that configurations with the same schema name can be

created.

The Mass transfer ID is used in the naming of SLT jobs and the system can

uniquely identify a schema.

The mapping of mass transfer IDs and related schema are stored in the SLT

control table DMC_MT_HEADER in the SAP LT Replication Server.

Qs. What are the jobs involved in replication process?

Following jobs are involved in replication process:

1. Master Job (IUUC_MONITOR_<MT_ID>)

2. Master Controlling Job (IUUC_REPLIC_CNTR_<MT_ID>)


3. Data Load Job (DTL_MT_DATA_LOAD_<MT_ID>_<2digits>)

4. Migration Object Definition Job (IUUC_DEF_MIG_OBJ_<2digits>)

5. Access Plan Calculation Job (ACC_PLAN_CALC_<MT_ID>_<2digits>)

Qs. What is the purpose of master job

(IUUC_MONITOR_<MT_ID>)?

Every 5 seconds, the monitoring job checks in the SAP HANA system whether

there are new tasks and, if so, triggers the master control jobs. It also deletes the

processed entries (tasks) from table RS_ORDER and writes statistics entries into

table RS_STATUS (in the relevant schema in the SAP HANA system).

Qs. What is the purpose of master controller job

(IUUC_REPLIC_CNTR_<MT_ID>)?

This job is scheduled on demand and is responsible for:

o • Creating database triggers and logging table in the source system

o • Creating synonyms

o • Writing new entries in admin tables in SLT server when a new table is

loaded/replicated

Qs. What is the purpose of Data Load Job

(DTL_MT_DATA_LOAD_<MT_ID>_<2digits>)?


This job should always be active. If the job does not complete successfully, the

master controller job restarts it.

This job is responsible for:

o • Loading data (load)

o • Replicating data (replication)

o • Changing status flag for entries in control tables in the SAP LT Replication

Server

Qs. What is the purpose of Migration Object Definition Job

(IUUC_DEF_MIG_OBJ_<2digits>)?

This job defines the migration object of a specific table (that you choose to

load/replicate), which is the fundamental object for LT replication. The migration

object definition should normally be quite fast for all tables.

Qs. What is the purpose of Access Plan Calculation Job

(ACC_PLAN_CALC_<MT_ID>_<2digits>)?

This job calculates the access plan of a specific table (that you choose to

load/replicate), and the access plan is used for data load or replication. The

access plan is also a fundamental object for the replication. For a normal sized

table, access plan calculation should finish quite quickly (less than 1 minute)

while large tables might take up to several hours to finish.


Qs. What is the relation between the number of data

transfer jobs in the configuration settings and the available

BGD work processes?

Each job occupies 1 BGD work processes in SLT replication server. For each

configuration, the parameter Data Transfer Jobs restricts the maximum number

of data load job for each mass transfer ID (MT_ID).

A mass transfer ID requires at least 4 background jobs to be available:

o • One master job

o • One master controller job

o • At least one data load job

o • One additional job either for migration/access plan calculation/to change

configuration settings in “Configuration and Monitoring Dashboard”.

Qs. If you set the parameter “data transfer jobs” to 04 in a

configuration “SCHEMA1”, a mass transfer ID 001 is

assigned. Then what jobs should be in the system?

o 1 Master job (IUUC_MONITOR_SCHEMA1)

o 1 Master Controller job (IUUC_REPL_CNTR_001_0001)


o At most 4 parallel jobs for MT_ID 001 (DTL_MT_DATA_LOAD_001_

01/~02/~03/~04)

Qs. What happens after the SLT replication is over?

The SLT replication server creates 1 user, 4 roles, 2 stored procedures and 8

tables.

o 1 User

o 1 Privilege

o 4 Roles

1. <REPLICATION SCHEMA>_DATA_PROV

2. <REPLICATION_SCHEMA>_POWER_USER

3. <REPLICATION_SCHEMA>_USER_ADMIN

4. <REPLICATION_SCHEMA>_SELECT

o 2 Stored procedures

1. RS_GRANT_ACCESS

2. RS_REVOKE_ACCESS

o 8 Tables

1. DD02L

2. DD02T

3. RS_LOG_FILES

4. RS_MESSAGES


5. RS_ORDER

6. RS_ORDER_EXT

7. RS_SCHEMA_MAP

8. RS_STATUS

Qs. What are the different replication scenarios?

Different replication scenarios are:

Load, Replicate, Stop, Suspend and Resume.

Load:

Starts an initial load of replication data from the source system. The procedure is

a one-time event. After it is completed, further changes to the source system

database will not be replicated.

For the initial load procedure, neither database triggers nor logging tables are

created in the source system. Default settings use reading type 3 (DB_SETGET)

with up to 3 background jobs in parallel to load tables in parallel or subsequently

into the HANA system.

Replicate:

Combines an initial load procedure and the subsequent replication procedure

(real time or scheduled).

Before the initial load procedure will start, database trigger and related logging

table are created for each table in the source system as well as in SLT replication

server.


Stop:

Stops any current load or replication process of a table.

The stop function will remove the database trigger and related logging tables

completely. Only use this function if you do want to continue a selected table

otherwise you must initially load the table again to ensure data consistency.

Suspend:

Pauses a table from a running replication. The database trigger will not be

deleted from the source system. The recording of changes will continue and

related information is stored in the related logging tables in the source system.

If you suspend tables for a long time the size of logging tables may increase and

adjust the table space if required.

Resume:

Restarts the application for a suspended table. The previous suspended

replication will be resumed (no new initial load required).

Qs. What happens if the replication is suspended for a long

period of time or system outage of SLT or HANA system?

The size of the logging tables increases.


Qs. How to avoid unnecessary logging information from

being stored?

Pause the replication by stopping the schema-related jobs.

Qs. Will the table size in SAP HANA database and in the

source system the same?

No.

As HANA database supports compression, the table size in SAP HANA may be

decreased.

Qs. When to go for table partitioning?

If the table size in HANA database exceeds 2 billion records, split the table by

using portioning features by using “Advanced replication settings” (transaction

IUUC_REPL_CONT, tab page IUUC_REPL_TABSTG).

Qs. Where do you define transformation rules?

By using “Advanced replication settings” (transaction IUUC_REPL_CONT, tab

page IUUC ASS RULE MAP)

Qs. Are there any special considerations if the source

system is non-SAP system?


The concept of trigger-based replication is actually meant for SAP source

systems.

In case of non-SAP system, following points should be kept in mind:

o There will be a database connection between non-SAP source and SLT

system instead of RFC.

o Source must have primary key

o Tables DD02L, DD02T which contains metadata are just initially loaded but

not replicated.

o The read modules reside on SLT system.

o Tables with database specific formats may need transformation rules

before they are replicated.

o Only SAP supported databases are supported as non-SAP source

systems.

Qs. Does SLT for SAP HANA support data compression

like SAP HANA database?

Yes, this is automatically covered by the RFC connection used for data

replication from the SAP source system.

Qs. What is SAP HANA Studio?

o The SAP HANA studio is an Eclipse-based development and administration

tool for working with HANA.


o It enables technical users to manage the SAP HANA database, to create

and manage user authorizations, to create new or modify existing models

of data etc.

o It is a client tool, which can be used to access local or remote HANA

system.

Qs. What are the different perspectives available in HANA

Studio?

Modeler:

Used for creating various types of views and analytical privileges.

SAP HANA Development:

Used for programming applications for creating development objects to access or

update data models such as Server-side Java script, XSJS, XSODATA files.

Administration:

Used to monitor the system and change settings.

Debug:

Used to debug code such as SQLScript (.procedure files) or Server-side Java

script (.xsjs files).

To open a perspective, go to Window → Open Perspective.


Qs. What are the supported platforms for HANA studio?

The SAP HANA studio runs on the Eclipse platform 3.6. We can use the SAP

HANA studio on the following platforms:

o • Microsoft Windows x32 and x64 versions of: Windows XP, Windows Vista,

Windows 7

o • SUSE Linux Enterprise Server SLES 11: x86 64-bit version

Note: For Mac OS, HANA studio is available but there is no HANA client for that.

Qs. What are the system requirements for HANA studio?

Java JRE 1.6 or 1.7 must be installed to run the SAP HANA studio. The Java

runtime must be specified in the PATH variable. Make sure to choose the correct

Java variant for installation of SAP HANA studio:

o • For a 32-bit installation, choose a 32-bit Java variant.

o • For a 64-bit installation, choose a 64-bit Java variant.

Qs. How to add new HANA system in HANA studio?

In order to connect to a SAP HANA system we need to know the Server Host ID

and the Instance Number. Also we need a Username & Password combination to

connect to the instance.

The left side Navigator space shows all the HANA system added to the SAP

HANA Studio.


Steps to add new HANA system:

1. Right click in the Navigator space and click on Add System

2. Enter HANA system details, i.e. the Hostname & Instance Number and click

Next.


3. Enter the database username & password to connect to the SAP HANA

database. Click on Next and then Finish.


4. The SAP HANA system now appears in the Navigator.


Qs. What is the difference between catalog and content?

In HANA Studio every HANA system has two main sub-nodes, Catalog and

Content.


Catalog:

o The Catalog represents SAP HANA’s data dictionary, i. e. all data

structures, tables, and data which can be used.

o All the physical tables and views can be found under the Catalog node.

Content:

o The Content represents the design-time repository which holds all

information of data models created with the Modeler.

o Physically these models are stored in database tables which are also

visible under Catalog. The Models are organized in Packages. The

Contents node just provides a different view on the same physical data.

o The created Column Views are always located in schema _SYS_BIC, their

metadata in schema _SYS_BI.

Qs. Does 32 bit version of HANA client work with SAP

HANA repository and SAP HANA Development

perspective?

There is no 32 bit version of the repository client.

If you want to make use of the repository integration features, for example, in the

Project Explorer view in the SAP HANA Development perspective, you must

install the 64 bit version of the repository client.


Qs. How can we set path to the repository client in HANA

Studio?

1. In SAP HANA studio, choose Window –> Preferences –> SAP HANA

Development –> Repository Access

2. Choose Browse and enter the path to the SAP HANA client executable,

regi.exe. For example, C:Program Filessaphdbclientregi.exe

3. Choose Apply to enable the new setting.

4. Choose OK to save the settings.


Qs. How to start HANA Studio in Linux?

To start the SAP HANA studio, perform the following steps:

1. Open a shell and go to the installation directory, such as /usr/sap/hdbstudio

2. Execute the following command “./hdbstudio”. The SAP HANA studio

starts.

3. To set the path to the repository client

1. In SAP HANA studio, choose Window Preferences SAP HANA

Development Repository Access

2. Choose Browse… to enter the path to the SAP HANA client

executable, regi. For example, /usr/sap/hdbclient

3. Choose Apply to enable the new setting.

4. Choose OK to save the settings.

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