1. Define Five-minute rule?
It is a rule of thumb
for deciding whether a data item should be kept in memory, or stored on disk
and read back into memory when required. The rule is “randomly accessed disk
pages of cache are re-used every 5 minutes”.
2. Define multi-core CPU?
Multiple CPU’s on one
chip or in one package is called multi-core CPU.
3. Define Stall?
Waiting for data to
be loaded from main memory into the CPU
cache is called as Stall.
4. What is SAP In-Memory Appliance (SAP HANA)?
4. What is SAP In-Memory Appliance (SAP HANA)?
HANA is an in-memory
technique to store data that is particularly suited for handling very large
amounts of tabular, or relational, data with extra ordinary performance. Common
databases store tabular data row-wise. Reorganizing the data in memory column-wise
brings a tremendous speed increase when accessing a subset of the data in each
table row.
5. What are the components or products
of HANA?
Ø SAP HANA contains the following components.
Ø SAP HANA DATABASE
Ø SAP HANA Studio SAP HANA CLIENT
Ø SAP HANA INFORMATION COMPOSER
Ø DIAGNOSTIC AGENT 7.3
Ø SAP HANA client package for MS excel
Ø SAP HANA UI for Information Access (INA)
Ø SAP HANA AFL 1.0
Ø Software Update Manager for SAP HANA
Ø SAP LT Replication Add On
Ø SAP LT Replication Server
Ø SAP HANA Direct Extractor Connection (DXC)
Ø SAP Data Services 4.0
6. What are the different editions
available in HANA appliance software?
ØPlatform Edition:
Platform
edition is intended for customers who want to use ETL-based replication and
already have a license for SAP BO Data Services.
ØEnterprise Edition:
Enterprise
edition is intended for customers who want to use either trigger-based
replication or ETL-based replication and do not already have all of the
necessary licenses for SAP BO Data Services.
7. What is columnar and Row-Based Data
Storage?
A database
table contains data in the form of rows and columns. However Computer memory is
organized as a linear structure. To store a table in linear memory, there are
two options. A row-based storage stores a table as a sequence of records, each
of which contains the fields of one row.
In a columnar storage the entries of a column are stored in contiguous
memory locations. The SAP HANA database allows specifying whether a table is to
be stored column-wise or row-wise. It is also possible to alter an existing
table from columnar to row-based and vice versa. Search operations in tabular
data can be accelerated by organizing data in columns instead in rows.
8. What are the advantages of Column
based tables?
Ø Calculations are typically executed on single
or a few columns only.
Ø The table is searched based on values of a
few columns.
Ø The table has a large number of columns.
Ø The table has a large number of rows and
columnar operations are required
(aggregate, scan, etc.).
Ø High compression rates can be achieved
because the majority of the columns contain only few distinct values (compared
to number of rows).
9. What are the advantages of Row-based
tables?
Ø The application needs
to only process a single record at one time (many selects and/or updates of
single records).
Ø The application
typically needs to access a complete record (or row).
Ø The columns contain
mainly distinct values so that the compression rate would be low.
Ø Neither aggregations
nor fast searching are required.
Ø The table has a
small number of rows (e. g. configuration tables).
10. Which case the data to be stored in
columnar storage?
To enable fast
on-the-fly aggregations, ad-hoc reporting, and to benefit from compression
mechanisms it is recommended that transaction data to be stored in a
column-based table.
11. What is paralisation?
Column-based
storage makes it easy to execute operations in parallel using multiple
processor cores. In a column store data is already vertically partitioned 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
12. What are the different Compression
Techniques?
1. Run-length
encoding
2. Cluster
encoding
3. Dictionary
encoding
13.
Why materialized aggregates are not required?
With a scanning
speed of several gigabytes per millisecond, in-memory column stores, make it
possible to calculate aggregates on large amounts of data on the fly with high
performance. This is expected to eliminate the need for materialized aggregates
in many cases.
14. What are the advantages of
Eliminating materialized aggregates?
Ø Simplified data
model
Ø Simplified
application logic
Ø Higher level of
concurrency and With the fly Aggregation we have aggregated values up to date
15. What are the different types of
replication techniques?
Ø ETL based replication
using BODS
Ø Trigger based
replication using SLT
Ø Extractor based data
acquisition using DXC
16. Define SLT?
SLT stands for
SAP Landscape Transformation which is a trigger based replication. SLT
replication server is the replication technology to pass data from source
system to the target system. The source can be either SAP or non-SAP. Target
system is SAP HANA system which contains HANA database.
17. What is Configuration in SLT?
The
information to create the connection between the source system, SLT system, and
the SAP HANA system is specified within the SLT system as a Configuration. You
can define a new configuration in Configuration & Monitoring Dashboard
(transaction LTR).
18. 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).
Ø Status Yellow: It
may occur due to triggers which are not yet created successfully.
Ø Status Red: It may
occur if master job is aborted (manually in transaction SM37).
19. What is advanced replication
settings?
A transaction
that runs on SLT replication server to specify advanced replication settings
like
a. Modifying
target table structures,
b. Specifying
performance optimization settings
c. Define
transformation rules
20. Define Latency?
It is the
length of time to replicate data (a table entry) from the source system to the
target system.
21. Define 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.
22. 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
Ø Convert fields
Ø Fill empty fields
Ø Skip records
23. When to change the number of Data
Transfer job?
If the speed of
the initial load/replication latency time is not satisfactory If SLT
replication server has more resources than initially available, we can increase
the number of data transfer and/or initial load jobs. After the completion of
the initial load, we may want to reduce the number of initial load jobs.
—
24. 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).
25. What are the jobs involved in
replication process?
Ø Master Job
(IUUC_MONITOR_<MT_ID>)
Ø Master Controlling
Job (IUUC_REPLIC_CNTR_<MT_ID>)
Ø Data Load Job
(DTL_MT_DATA_LOAD_<MT_ID>_<2digits>)
Ø Migration Object
Definition Job (IUUC_DEF_MIG_OBJ_<2digits>)
Ø Access Plan
Calculation Job (ACC_PLAN_CALC_<MT_ID>_<2digits>)
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