SAP HANA Interview Questions

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SAP HANA INTERVIEW QUESTIONS
1. State the different types of replication
techniques? The three types are as below ETL
based replication using BODS Trigger based
replication using SLT Extractor based data
acquisition using DXC
2. What is SLT? The full form of SLT is SAP
Landscape Transformation which is nothing but a
trigger based replication. It is the replication
technology to pass the data from the source
system to the target system. Here the source can
be either SAP or non-SAP whereas the Target
system is SAP HANA system which contains
HANA database.
3. Can we load and replicate data from one source
system to multiple target database schemas of
HANA system? Yes. It can be loaded and replicated
for up to 4.
4. Can the type of data load and replication be
specified? It can be either in real time, or
scheduled by time or by interval.
5. Define Configuration in SLT? The information
required to create the connection between the
source system, SLT system, and the SAP HANA
system is specified within the SLT system as a
Configuration. A new configuration in
Configuration Monitoring Dashboard (transaction
LTR) can hence be defined.
6. Is there any need of pre-requisite before
creating the configuration and replication? DMIS
add-on is installed in SLT replication server for
SAP source systems. The role IUUC_REPL_REMOTE is
assigned to the user for RFC connection but not
DDIC. DMIS add-on is not required and grants a
database user sufficient authorization for data
replication for a non-SAP source system.
7. Define what is Configuration and Monitoring
Dashboard? They are applications that run on SLT
replication server to specify configuration
information (such as source system, target
system, and relevant connections) so that data
can be replicated. The replication status
(transaction LTR) can also be monitored. Status
Yellow occurs due to triggers which are not yet
created successfully. Status Red occurs if master
job is aborted (manually in transaction SM37).
8. What is advanced replication
settings? Advanced Replication settings is a
transaction that runs on SLT replication server
to specify advanced
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replication settings like modifying target table
structures, specifying performance optimization
settings that defines transformation rules.
9 Define Latency? Latency is the length of time
to replicate data (a table entry) from the source
system to the target system.
10. What is logging table? A logging table in the
source system that can record any changes to a
table that is being replicated. This thereby
ensures that SLT replication server can replicate
these changes to the target system.
11. What are Transformation rules? Transformation
rule is a rule specified in the Advanced
Replication settings transaction for source
tables such a way that the data is transformed
during the replication process. For example one
can specify rule to Convert fields, Fill empty
fields and Skip records
12. When a new configuration is set up what
happens? The database connection is automatically
created along with GUID and Mass transfer id
(MT_ID). Configurations with the same schema
name can be created which is ensured by schema
GUID. The naming of SLT jobs and the system can
uniquely identify a schema where the Mass
transfer ID is used.
13. What are the factors that influence the
change/increase the number of jobs? The factors
that influence the change or increase in the
number of jobs are number of configurations
managed by the SLT replication server, number of
tables to be loaded/ replicated for each
configuration, expected speed of initial load,
expected replication latency time. As a thumb
rule, one BDG job should be used for each 10
tables in replication to achieve acceptable
latency times.
14. When is the number of Data Transfer jobs
changed? The number of data Transfer jobs changes
when the speed of the initial load/replication
latency time is not satisfactory, if SLT
replication server has more resources than that
is initially available. The number of initial
load jobs may be reduced after the completion of
the initial load
15. Mention the jobs involved in replication
process? The main jobs involved in the
replication process are stated as below Master
Job (IUUC_MONITOR_ltMT_IDgt) Master Controlling Job
(IUUC_REPLIC_CNTR_ltMT_IDgt) Data Load Job
(DTL_MT_DATA_LOAD_ltMT_IDgt_lt2digitsgt) Migration
Object Definition Job (IUUC_DEF_MIG_OBJ_lt2digitsgt
) Access Plan Calculation Job (ACC_PLAN_CALC_ltMT_I
Dgt_lt2digitsgt)
16. State the relation between the number of data
transfer jobs in the configuration settings and
the available BGD work processes? In SLT
replication server each job occupies 1 BGD work
processes and for each configuration, the
parameter Data Transfer Jobs would restrict the
maximum number of data load job for each mass
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transfer ID (MT_ID). At least 4 background jobs
are required for a mass transfer ID requires to
be available. They are One master job , One
master controller job ,At least one data load job
,One additional job either for migration/access
plan calculation/to change configuration settings
in Configuration and Monitoring Dashboard.
17. If the parameter set for data transfer jobs
to 04 in a configuration SCHEMA1, a mass
transfer ID 001 is assigned. In such a case what
jobs should be in the system? The jobs should be
1 Master job (IUUC_MONITOR_SCHEMA1), 1 Master
Controller job (IUUC_REPL_CNTR_001_0001) and at
most 4 parallel jobs for MT_ID 001
(DTL_MT_DATA_LOAD_001_ 01/02/03/04) If at the
same time lots of tables are selected for load /
replication, there could be a chance that there
are not enough background jobs available to
start the load procedure for all tables
immediately. In such a case the number of
initial load jobs can be increased, or else
tables will be handled sequentially. For tables
with large volume of data the transaction
Advanced Replication Settings (IUUC_REPL_CONT)
to further optimize the load and replication
procedure for dedicated tables can be used.
18. After the SLT replication is over what
happens? After the replication is over, the SLT
replication server creates 1 user, 4 roles, 2
stored procedures and 8 tables as mentioned
below 1 User 1 Privilege 4 Roles ltREPLICATION
SCHEMAgt_DATA_PROV ltREPLICATION_SCHEMAgt_POWER_USER
ltREPLICATION_SCHEMAgt_USER_ADMIN ltREPLICATION_SCHEM
Agt_SELECT 2 Stored procedures RS_GRANT_ACCESS,
RS_REVOKE_ACCESS 8 Tables DD02L, DD02T,
RS_LOG_FILES, RS_MESSAGES, RS_ORDER,
RS_ORDER_EXT, RS_SCHEMA_MAP, RS_STATUS
19. State the different replication
scenarios? The different replication scenarios
are Load, Replicate, Stop, Suspend and
Resume. Before any application table is selected,
the initial load of the tables DD02L, DD02T
DD08L must be completed as they contain the
metadata information. Load This starts an
initial load of replication data from the source
system. The complete procedure is a one-time
event. Once completed, further changes to the
source system database will not be replicated.
Also for the initial load procedure, neither
database triggers nor logging tables are created
in the source system. The 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 This combines an initial load
procedure and the subsequent replication
procedure (real time or
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scheduled). Before the start of initial load
procedure, trigger of database and related
logging table are created for each table in the
source system as well as in SLT replication
server. Stop Replication This stops any current
load or replication process of a table. The stop
function removes the database trigger and related
logging tables completely. This function is used
only if you want to continue a selected table
otherwise it must be initially loaded again to
ensure data consistency. Suspend This pauses a
table from a running replication. Also the
database trigger will not be deleted from the
source system. The recording of changes would
continue and the related information would be
stored in the related logging tables in the
source system. If tables are suspended for a long
time the size of logging tables may increase and
adjust the table space if required. Resume This
restarts the application for a suspended table.
The previous suspended replication will
be resumed (no new initial load required).
20. If the replication is suspended for a long
period of time or system outage of SLT or HANA
system what would happen? The size of the logging
tables increases.
21. How can unnecessary logging information from
being stored be avoided? Unnecessary logging
information storage can be avoided by pausing the
replication which is by stopping the
schema-related jobs.
22. Are the table size in SAP HANA database and
in the source system the same? No they are not
same as HANA database supports compression.
23. When is table partitioning opted? If the
table size in HANA database exceeds 2 billion
records, the table should be splitted by
using portioning features by using Advanced
replication settings (transaction
IUUC_REPL_CONT, tab page IUUC_REPL_TABSTG).
24. Where are transformation rules
defined? Transformation rules are defined by
using Advanced replication settings
(transaction IUUC_REPL_CONT, tab page IUUC ASS
RULE MAP)
25. If the source system is non-SAP system, are
there any special considerations? The
trigger-based replication concept is actually
meant for SAP source systems. The main
differences are as below a) There would be a
database connection between non-SAP source and
SLT system instead of RFC. b) Source must have
primary key c) Tables DD02L, DD02T which contains
metadata are just initially loaded but not
replicated. d) The read modules resides on SLT
system. e) Tables with database specific formats
may need transformation rules just before they
are replicated.
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f) Only SAP supported databases (with respective
DBSL for SAP Net Weaver 7.02) are supported as
non- SAP source systems.
26. State the potential issues in the creation of
a configuration? The most potential issues in the
configuration creation is the missing add-on
DMIS_2010 in source system, missing the proper
role of SAP_IUUC_REPL_REMOTE for RFC user (
SAP_IUUC_USER for SLT system ) and if the Logon
credentials are not correct
27. How is it ensured that data is consistent in
source system and HANA system? Since any changes
in the source system that occurs is tracked in
the dedicated logging tables, the replication
status for each changed data record will be
transparent. An entry of logging table is deleted
after an every successful commit statement from
HANA database and this procedure ensures the
data consistency between source system and HANA
system.
28. Does SLT for SAP HANA support data
compression like SAP HANA database? Yes SLT for
SAP HANA supports data compression like SAP HANA
database and this is automatically covered by the
RFC connection used for data replication from the
SAP sour.
29. What are the product names in SAP HANA? In
short answer it's a mystery. A lot of changes
have happened around SAP and now its called SAP
HANA Appliance, SAP HANA Database and SAP HANA
Studio. All applications built on HANA will be
marked "powered by SAP HANA". And this is
probably to be changed again.
30. What is SAP HANA Appliance 1.0? SAP HANA 1.0
is an analytics appliance which consists of
certified hardware, and In Memory
DataBase (IMDB), an Analytics Engine and some
tooling for getting data in and out of HANA. The
logic and structures are built by the user and a
tool is used e.g. SAP BusinessObjects, to
visualize or analyze data.
31. State the limitations of HANA 1.0? The
limitations are very less. It can only replicate
certain data from certain databases and in
certain formats using the Sybase Replication
Server. The Batch loading is done using SAP
BusinessObjects Data Services 4.0 and is
optimized only for SAP Business Objects BI 4.0
reporting.
32. What is SAP HANA 1.5, 1.2 or 1.0 SP03? They
are all the same thing, and 1.0 SP03 is touted to
be the final name which should go into RampUp
(beta) in Q4 2011. This allows any SAP NetWeaver
BW 7.3 Data Warehouse to be migrated into a HANA
appliance. HANA 1.0 SP03 specifically also
accelerates BW calculations and planning, which
means even more performance gains can be attained.
33. Differentiate between HANA and IMDB? HANA is
the name for the current BI appliance (HANA 1.0)
and the BW Data Warehouse appliance (HANA 1.0
SP03). Both use the SAP IMDB Database Technology
(SAP HANA Database) as their underlying RDBMS.
SAP can be expected to start to differentiate
this more clearly as it starts to position the
technology for use cases other than Analytics.
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34. If NetWeaver BW can be run on IMDB/HANA, why
can't the Business Suite/ERP 6.0 be run too? This
is because it's not mature enough to support
business critical applications. From a technology
perspective, it is anyways possible to run the
Business Suite on IMDB and SAP has trialed moving
some large databases into IMDB already.
35. What is HANA excellent at? The most important
thing to note is, HANA brings to the table is the
ability to aggregate large data volumes in near
real-time - and to have the data updated in near
real-time. Demos show hundreds of billions of
records of data being aggregated in a matter of
seconds. Hence SAP has built a set of Analytics
Apps on top of HANA and these are set to be
great point use cases to get customers up and
running quickly.
36. What is HANA not good at? Some current issues
have been notices around HANA when delivering
ad-hoc analytics, especially when using the SAP
BusinessObjects Webi tool. No doubt that the
problem is that one can ask computationally very
difficult questions with Webi, which causes very
long response times with HANA. SAP needs to build
optimization for both Webi and HANA to reduce the
computational complexity of these questions.
37. What is the cost of HANA? The licensing cost
of HANA is not confirmed b SAP but the hardware
is somewhere around 1-200k per TB. In addition
to these licensing costs this is still being made
on a per-customer basis.
38. What is the reason for the speed of HANA? The
information can be retrieved from Regular RDBMS
technologies put the information on spinning
plates of iron (hard disks). The information is
stored in electronic memory, which is some 50x
faster (depending on how you calculate). It
stores a copy on magnetic disk, in case of power
failure or the like. Also to add in, most SAP
systems have the database on one system and a
calculation engine on another, and the
information is passed between them. With HANA,
this all happens within the same machine.
39. Is Oracle replaced by HANA/IMDB? Once the
Business Suite runs on IMDB, Oracle will not be
needed form any more by SAP customers who
purchase HANA. The short term is not affected
because even if HANA is bought today it still
needs an Oracle ERP system.
40. State the 101 compression with HANA when
compared to Oracle? When a typical uncompressed
Oracle or Microsoft SQL Server database is put
into HANA, it will be 10x smaller than before
and this is because of the way that HANA stores
information in a compressed format. Most
databases are now compressed and these numbers
may not fit every scenario, and to add to this
2x the RAM as your database is needed including a
plus room for growth. Sizing of HANA is still
a dark art.
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41. What is meant by buy a HANA only 2.5x
smaller than my big Oracle RDBMS? How about
archiving and data ageing? In some instances HANA
appliance that is only 2.5x smaller than it would
be under Oracle and only this can be bought. Data
ageing is not a part of the 1.0 release, but SAP
is certainly working on it.
42. What's the extended market opportunity for
IMDB? A few analysts seem to have tapped on that
the wider market opportunity which is believed to
be huge. Not only SAP applications but any third
party that requires ultra-high speed. Its not
just an appliance but a development platform.
43. What hardware is supported in SAP HANA right
now? All of the major vendors e.g. HP, IBM, Dell,
are offering HANA now. Technically HANA will run
on any Intel x64 based system from your laptop
through to the big 40-core, 2TB RAM servers. It
is however only supported on a small number of
big rack-mount servers like the Dell R910 and HP
DL980.
44. Does HANA run on blades? If not why? It's
still not clear but probably because the blades
doesnt yet offer the same performance. HANA is
optimized for the Intel X7560 CPU and runs
fastest on this. For instance, the Dell M910
blade can only run 2x X7650 CPUs and 512Gb RAM
in this configuration, which probably explains
the limitations. One thing is sure that HANA will
eventually run on blades as it's born to run on
blade technology.
45. CAN SAP make their own IMDB/HANA hardware? It
can but only in the labs so far. No such public
plans to compete against IBM/HP/Dell is there in
this space, but it could make sense for SAP to
enter the appliance market, especially in the
context of Data Centers and even more so in the
context of the SAP Business by Design cloud
offering, which will run on IMDB.
46. How big does HANA scale? Theory wise at least
very well. Most mid-size workloads - 2TB of
in-memory storage is equivalent to 5- 20TB of
Oracle storage can be run by the biggest single
server HANA hardware. HANA works in a way that
means it is possible to chain multiple systems
together which means that scalability has
thus-far been determined by the size of
customers' wallets. Whilst SAP talk up "Big Data"
quite a lot, HANA currently only scales to the
small-end of Big Data referring to the kind of
huge datasets that FaceBook or Google have to
store - not Terabytes, but rather Petabytes.
47. HANA uses which storage subsystem? A shared
network attached and varies from vendor to vendor
and is called the storage. Here both regular
magnetic disks and SSD storage can be used for
the backup of the database (HANA runs in memory
remember, so disk storage is just for backup,
and later, for data ageing). If the operator
require 2x storage that you have RAM, which is
2x the database size - i.e. storage size 4x
database size. Anyways in most cases there is
additional ultra-high speed SSD storage for log
files.
48. HANA support in real-time what types of
source database? If Sybase Replication Server
(SRS) for near real-time data is used then the
licensing still (SAP have license
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deals pending) needs to checked. If DB2 is run
then its fine but with Oracle and Microsoft SQL
Server there are some license challenges. So if
license is bought through SAP, because you may
have a limited license that does not allow
extraction.
49. For batch loads what source databases does
HANA support? If SAP BusinessObjects Data
Services 4.0 is used for bulk loads then it would
be the best. BO-DS is a very flexible Extract,
Transform Load tool that can support many
databases
50. What additional limitations does Sybase
Replication Server present? SRS has additional
restrictions which are worth to be understood. It
only replicates Unicode data and does not support
IBM DB2 compress tables.
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