Top 20+ Servlet Interview Questions & Answers [ J2EE TRICKS ]
Last updated on 04th Jul 2020, Blog, Interview Questions
These Servlet Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of Servlet As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer .we are going to cover top 100 Servlet Interview questions along with their detailed answers. We will be covering Servlet scenario based interview questions Servlet interview questions for fresher’s as well as Servlet interview questions and answers for experienced
1) What is Servlet? What is the purpose of it?
Servlet stands for Business Information Warehouse, also known as business intelligence. For any business, data reporting, analyses and interpretation of business data is very crucial for running business smoothly and making decision. Servlet manage the data and enables to react quickly and in line with the market. It enables the user to analyze data from operative Servlet applications as well as from other business.
2) What are the main areas and activities in Servlet?
a) Data Warehouse: Integrating, collecting and managing entire companys data.
b) Analyzing and Planning: Using the data stored in data warehouse.
c) Broad cast publishing: To send the information to the employees using email, fax etc.
d) Reporting: BI provides the tools for reporting in web-browser, excel etc
3) What all data sources you have used to acquire data in Servletsystem?
- Servlet systems (SAP Applications.
- Relational Database (Oracle, SQL Server, etc.)
- Flat File (Excel, Notepad)
- Multidimensional Source systems (Universe using UDI connector)
- Web Services that transfer data to BI by means of push
4) What is an InfoPackage?
An InfoPackage is used to specify how and when to load data to BI system from different data sources. An InfoPackage contains all the information how data is loaded from source system to a data source or PSA. InfoPackage consists of condition for requesting data from a source system.
Note that using an InfoPackage in BW 3.5, you can load data in Persistence Staging Area and also in targets from source system but If you are using SAP BI 7.0 data load should be restricted to PSA only for latest versions.
5) What is table partition?
Table partition is done to manage the huge data to improve the efficiency of the applications. The partition is based on 0CALMONTH and 0FISCPER. There are two type of partitioning that is done
6) What are the features of multi provider?
a) It doesnt contain any type of data.
b) The data comes completely from the information which is provided.
c) By union operations the info providers are connected.
Data flows from a transactional system to the analytical system (BW). DS ( Data Service) on the transactional system needs to be replicated on BW side and attached to info source and update rules respectively.
7) What is ODS (Operational Data Store)?
‘Operational Data Store’ or ‘ODS’ is used for detailed storage of data. It is a BW architectural component that appears between PSA ( Persistent Staging Area) and infocubes, it allows BEX (Business Explorer) reporting. It is primarily used for detail reporting rather than dimensional analysis, and it is not based on the star schema. ODS (Operational Data Store) objects do not aggregate data as infocubes do. To load the data into an IDS object, new records are inserted, existing records are updated, or old records are deleted as specified by RECORDMODE value.
8)What is an Info Object and why it is used in Servlet?
Info Objects are known as smallest unit in and are used in Info Providers, DSOs, Multi providers, etc. Each Info Provider contains multiple Info Objects. Info Objects are used in reports to analyze the data stored and to provide information to decision makers.
9) How do you access to source system data in BI without extraction?
To access data in BI source system directly. You can directly access to source system data in BI without extraction using Virtual Providers. Virtual providers can be defined as InfoProviders where transactional data is not stored in the object. Virtual providers allow only read access on BI data.
10) What is the use of Transformation and how the mapping is done in BW?
Transformation process is used to perform data consolidation, cleansing and data integration. When data is loaded from one BI object to other BI object, transformation is applied on the data. Transformation is used to convert a field of source into the target object format.
Transformation rules − Transformation rules are used to map source fields and target fields. Different rule types can be used for transformation.
11) What is UD connect in Servlet system? How does it allow reporting in BI system?
Universal data UD connect allows you to access Relational and multidimensional data sources and transfer the data in form of flat data. Multidimensional data is converted to flat format when Universal Data Connect is used for data transfer. UD uses J2EE connector to allow reporting on SAP and non-SAP data. Different BI Java connectors are available for various drivers, protocols as resource adapters −
- BI ODBO Connector
- BI JDBC Connector
- BI SAP Query Connector
- XMLA Connector
12)What is the difference between ODS and Info-cubes?
The difference between ODS and Info-cubes are
- ODS has a key while Info-cubes does not have any key
- ODS contains detailed level data while Info-cube contains refined data
- Info-cube follows Star Schema (16 dimensions) while ODS is a flat file structure
- There can be two or more ODS under a cube, so cube can contain combined data or data that is derived from other fields in the ODS
13) How many data types are there in characteristics info object?
There are 4 data types:
14) What are the T-codes for Info-cubes?
The T-codes for Info-Cubes are
a) LISTSCHEMA: Show InfoCube schema
b) LISTCUBE: List viewer for InfoCubes
c) RSDCUBE, RSDCUBED, RSDCUBEM: Start InfoCube editing
15) Write the types of Multi-providers?
The types of Multi-providers are:
a) Heterogeneous Multi providers: These info-providers only have a few number of characteristics and key figures. It can be used for the modelling of scenarios by dividing them into sub-scenarios. Each sub-scenario is represented by its own info-provider.
b) Homogeneous Multi providers: It consists of technically identical info-providers, such as infocubes with exactly the same characteristics and key figures.
16) What do you understand by data target administration task?
Data target administration task includes
a) Complete deletion of data target
b) Construct database statistics
c) Generate Index
d) Delete Index
17) What is B/W statistics and how it is used?
The sets of cubes delivered by SAP are used to measure performance for query, loading data etc. B/W statistics as the name suggests is useful in showing data about the costs associated with the B/W queries, OLAP, aggregative data etc.
18)Define multi-provider in SAP BI ? What are the features of Multiproviders?
Multi-provider is a type of info-provider that contains data from a number of info-providers and makes it available for reporting purposes.
Multi-provider does not contain any data.
- The data comes entirely from the info providers on which it is based.
- The info-providers are connected to one another by union operations.
- Info-providers and Multi-providers are the objects or views relevant for reporting.
- A multi-provider allows you to run reports using several info-providers that are, it is used for creating reports for one or more than one info-provider at a time.
19)What is BEx Map in SAP BI?
BEx Map is BWs Geographical Information System (GIS). BEx Map is one of the characteristics for SAP BI, and it gives the geographical information like customer, customer sales region and country.
20)What is the t-code to see log of transport connection?
In RSA1 ->Transport Connection you can collect the Queries and the Role and after this you can transport them (enabling the transport in SE10, import it in STMS
21)Difference between v1, v2, v3 jobs in extraction?
V1 Update: whenever we create a transaction in R/3(e.g.Sales Order) then the entries get into the R/3 Tables (VBAK, VBAP..) and this takes place in V1 Update.
V2 Update: V2 Update starts a few seconds after V1 Update and in this update the values get into Statistical Tables, from where we do the extraction into BW.
V3 Update: Its purely for BW extraction.
22) What are statistical update and document update?
Synchronous Updating (V1 Update)
The statistics update is made synchronously with the document update.
While updating, if problems that result in the termination of the
statistics update occur, the original documents are NOT saved. The cause
of the termination should be investigated and the problem solved.
Subsequently, the documents can be entered again.Radio button: V2 updating
23)Do you have any idea how to improve the performance of the BW?
Asynchronous Updating (V2 Update)
With this update type, the document update is made separately from the statistics update. A termination of the statistics update has NO influence on the document update (see V1 Update).
Radio button: Updating in U3 update program
Asynchronous Updating (V3 Update)
With this update type, updating is made separately from the document update. The difference between this update type and the V2 Update lies, however, with the time schedule. If the V3 update is active, then the update can be executed at a later time.
In contrast to V1 and V2 Updates, no single documents are updated. The V3 update is, therefore, also described as a collective update.
24)How can you decide the query performance is slow or fast?
You can check that in RSRT tcode.
execute the query in RSRT and after that follow the below steps
Go to SE16 and in the resulting screen give table name as RSDDSTAT for BW 3.x and RSDDSTAT_DM for BI 7.0 and press enter you can view all the details about the query like time taken to execute the query and the timestamps
25)What is statistical setup and what is the need and why?
Go to transaction code RSA3 and see if any data is available related to your DataSource. If data is there in RSA3 then go to transaction code LBWG (Delete Setup data) and delete the data by entering the application name.
Go to transaction SBIW –>Settings for Application Specific Datasource –>Logistics –>Managing extract structures –>Initialization –>Filling the Setup table –>Application specific setup of statistical data –>perform setup (relevant application)
In OLI*** (for example OLI7BW for Statistical setup for old documents: Orders) give the name of the run and execute. Now all the available records from R/3 will be loaded to setup tables.
Go to transaction RSA3 and check the data.
Go to transaction LBWE and make sure the update mode for the corresponding DataSource is serialized V3 update.
26)Why we have construct setup tables?
The R/3 database structure for accounting is much more easier than the Logistical structure.
Once you post in a ledger that is done. You can correct, but that give just another posting.
BI can get information direct out of this (relatively) simple database structure.
In LO, you can have an order with multiple deliveries to more than one delivery addresses. And the payer can also be different.
When 1 item (order line) changes, this can have its reflection on order, supply, delivery, invoice, etc.
27)How can you eliminate the duplicate records in TD, MD?
Try to check the system logs through SM21 for the same.
28) Explain the architecture of SAP BW system and its components
Process designer and other functions.
Business Explorer BEx is reporting and analysis tool that support query, analysis and reporting functions in BI. Using BEx, you can analyze historical and current data to different degree of analysis.
29) What is an InfoObject and why it is used in Servlet?
Info Objects are known as smallest unit in SAP BI and are used in Info Providers, DSOs, Multi providers, etc. Each Info Provider contains multiple Info Objects.
InfoObjects are used in reports to analyze the data stored and to provide information to decision makers.
30)What are the different categories of InfoObjects in BW system?
Info Objects can be categorized into below categories −
Characteristics like Customer, Product, etc.
Units like Quantity sold, currency, etc.
Key Figures like Total Revenue, Profit, etc.
Time characteristics like Year, quarter, etc.
31) What is the use of Infoarea in SAP BW system?
Info Area in SAP BI are used to group similar types of object together. Info Area are used to manage Info Cubes and Info Objects. Each Info Objects resides in an Info Area and you can define it a folder which is used to hold similar files together.
32) What is a ‘Fact Table’?
Fact table is the collection of facts and relations that mean foreign keys with the dimension. Actually fact table holds transactional data.
33)What are different types on Virtual providers?
VirtualProviders based on DTP
VirtualProviders with function modules
VirtualProviders based on BAPIs
34) Which Virtual Providers are used in which scenario of data extraction?
VirtualProviders based on DTP −
This type of Virtual Providers are based on the data source or an Info Provider and they take characteristics and key figures of source. Same extractors are used to select data in source system as you use to replicate data into BI system.
35) When to Virtual Providers based on DTP?
When only some amount of data is used.
You need to access up to date data from a SAP source system.
Only few users executes queries simultaneously on the database.
36)Virtual Provider with Function Module −
This Virtual Provider is used to display data from non BI data source to BI without copying the data to BI structure. The data can be local or remote. This is used primarily for SEM application.
37)What are the extractors and mention their types?
To extract data from the system program is used which is known as Extractor. The types of extractors in BW are:
a) Application Specific: BW content FI, HR, CO, SAP CRM, LO cockpit
b) Customer-Generated Extractors: LIS, FI-SL, CO-PA
c) Cross Application (Generic Extractors) : DB View,Infoset, Function Module
38) How do perform real time data acquisition in BW system?
Real time data acquisition is based on moving data to Business Warehouse in real time. Data is sent to delta queue or PSA table in real time.
39) What is InfoObject catalog?
InfoObjects are created in Info Object catalog. It is possible that an Info Object can be assigned to different Info Catalog.
40) What is the use DSO in BW system? What kind of data is stored in DSOsWhat are the different components in DSO architecture?
To access data for reporting and analysis immediately after it is loaded,
41) What all data sources you have used to acquire data in SAP BW system?
SAP systems (SAP Applications/SAP ECC)
Relational Database (Oracle, SQL Server, etc.)
Flat File (Excel, Notepad)
Multidimensional Source systems (Universe using UDI connector)
Web Services that transfer data to BI by means of push
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42)What is meant by conversions and how will you track conversions through GA?
One of the important questions suggested by most of Google analytics questions and answer guides. Conversions happen when your predefined Google Analytics goals are accomplished thus generating ROI to the website.
For example, if the user takes any desired action on the website, like filling the form or signing up a newsletter, or simply showing a high level of engagement, etc. Goals can be utilized in Google analytics to set the conversion tracking.
43) What are the three elements of Event Tracking?
Three elements of event tracking are-
44) What is RPC in Analytics?
RPC stands for Revenue Per Clicks is an e-commerce metric available in Google analytics. Which simply says the value of each click. With the help of RPC, you can identify the keywords which are affecting your campaign. It is not a common google analytics question but can be asked sometimes to check your in-depth knowledge.
45) What is Custom dimensions and metrics?
Custom dimensions and custom metrics are like default dimensions and metrics in your Google Analytics account, except they are created by you to collect and analyze data Analytics don’t track otherwise.
46) Explain the Reverse Goal Path Report in Analytics.
As the name implies, the report follows the user journey to the destination page. Reverse goal path report retraces the last three steps that the visitor took in finishing a goal. The report helps the webmaster to analyze the number of conversions generated by each conversion path. It provides a rewind replay of the journey.
47) What is site speed report in analytics?
A slow site can harm your website ranking. So, it’s important to have good website speed. To collect site speed data, Go to reports, select behavior > site speed. Site speed reports show how quickly your website loads and ready to interact with visitors. It helps you to identify the areas to be improved.
The Site Speed reports measure three aspects of latency:
48) How to avoid spam in GA?
We can filter out this data from spam sources.
49) How much customization possible in Analytics?
We can customize the GA but not as a whole. Few features and modules can be customized according to our needs.
50) What is the use of Time lag report?
Time lag report helps us to find the time lag in between the original session and completion of the goal.
51) When you are using SAP BI7.x, you can load the data to which component?
In BW 3.5, you can load data in Persistence Staging Area and also in targets from source system but If you are using SAP BI 7.0 data load should be restricted to PSA only for latest versions.
52) What is modelling?
Designing of data base is done by using modelling. The design of DB (Data Base) depends on the schema, and schema is defined as the representation of tables and their relationship.
53) What is extended Star schema? Which of the tables are inside and outside cube in an extended star schema?
In Extended Star schema, Fact tables are connected to Dimension tables and dimension table is connected to SID table and SID table is connected to master data tables. In Extended star schema you have Fact and Dimension tables are inside the cube however SID tables are outside cube. When you load the transactional data into Info cube, Dim Ids are generated based on SIDs and these Dim ids are used in fact tables.
54) How extended Star schema is different from Star schema?
In Extended Star schema one fact table can connect to 16 dimensions tables and each dimension table is assigned with 248 maximum SID tables. SID tables are also called Characteristics and each characteristic can have master data tables like ATTR, Text, etc.
In Star Schema, Each Dimension is joined to one single Fact table. Each Dimension is represented by only one dimension and is not further normalized.
Dimension Table contains set of attribute that are used to analyze the data.
55) which Data store object is used?
DataStore object for direct update allows you to access data for reporting and analysis immediately after it is loaded. It is different from standard DSOs in the way how it processed the data. Data is stored in same format in which it was loaded to DataStore object for direct update by the application.
56) Explain the structure of direct update DSOs?
one table for active data and no change log area exists. Data is retrieved from external systems using APIs.
Below APIs exists −
RSDRI_ODSO_INSERT: These are used to insert new data.
RSDRI_ODSO_INSERT_RFC: Similar to RSDRI_ODSO_INSERT and can be called up remotely.
RSDRI_ODSO_MODIFY: This is used to insert data having new keys.For data with keys already in the system, the data is changed.
RSDRI_ODSO_MODIFY_RFC: Similar to RSDRI_ODSO_MODIFY and can be called up remotely.
RSDRI_ODSO_UPDATE: This API is used to update existing data.
RSDRI_ODSO_UPDATE_RFC: This is similar to RSDRI_ODSO_UPDATE and can be called up remotely.
RSDRI_ODSO_DELETE_RFC: This API is used to delete the data.
57) Can we perform Delta uploads in direct update DSOs?
As structure of this DSO contains one table for active data and no change log so this doesnt allow delta update to InfoProviders.
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58) What is write optimized DSOs?
In Write optimized DSO, data that is loaded is available immediately for the further processing.
59) Where do we use Write optimized DSOs?
Write optimized DSO provides a temporary storage area for large sets of data if you are executing complex transformations for this data before it is written to the DataStore object. The data can then be updated to further InfoProviders. You only have to create the complex transformations once for all data.
Write-optimized DataStore objects are used as the EDW layer for saving data. Business rules are only applied when the data is updated to additional InfoProviders.
60) Explain the structure of Write optimized DSOs? How it is different from Standard DSOs?
It only contains table of active data and there is no need to activate the data as required with standard DSO. This allows you to process the data more quickly.
61) To perform a Join on dataset, what type of InfoProviders should be used?
Infosets are defined as special type of InfoProviders where data sources contains Join rule on DataStore objects, standard InfoCubes or InfoObject with master data characteristics. InfoSets are used to join data and that data is used in BI system.
62)What is a temporal join?
Temporal Joins: are used to map a period of time. At the time of reporting, other InfoProviders handle time-dependent master data in such a way that the record that is valid for a pre-defined unique key date is used each time. You can define Temporal join that contains atleast one time-dependent characteristic or a pseudo time-dependent InfoProvider.
63) Where do we use InfoSet in BI system?
Infosets are used to analyze the data in multiple InfoProviders by combining master data charactertics, DataStore Objects, and InfoCubes.
You can use temporal join with InfoSet to specify a particular point of time when you want to evaluate the data.
You can use reporting using Business Explorer BEx on DSOs without enabling BEx indicator.
64) What are the different type of InfoSet joins?
Left Outer Join
65) What is the use of InfoCube in BW system?
InfoCube is defined as multidimensional dataset which is used for analysis in a BEx query. An InfoCube consists of set of relational tables which are logically joined to implement star schema. A Fact table in star schema is joined with multiple dimension tables.
You can add data from one or more InfoSource or InfoProviders to an InfoCube. They are available as InfoProviders for analysis and reporting purposes.
66) What is the structure of InfoCube?
An InfoCube is used to store the data physically. It consists of a number of InfoObjects that are filled with data from staging. It has the structure of a star schema.
In SAP BI, an Infocube contains Extended Star Schema as shown above.
An InfoCube consists of a fact table which is surrounded by 16 dimension tables and master data that is lying outside the cube.
67) What is the use of real time InfoCube? How do you enter data in real time InfoCubes?
Real time InfoCubes are used to support parallel write access. Real time InfoCubes are used in connection with the entry of planning data.
You can enter the data in Real time InfoCubes in two different ways −
Transaction for entering planning data
68) How do you create a real time InfoCube in administrator workbench?
A real time InfoCube can be created using Real Time Indicator check box.
69) Can you make an InfoObject as info provider and why?
Yes, when you want to report on charactertics or master data, you can make them as InfoProvider.
70) Is it possible to convert a standard InfoCube to real time InfoCube?
To convert a standard InfoCube to real time InfoCube, you have two options −
Convert with loss of Transactional data
Conversion with Retention of Transaction Data
71) Can you convert an InfoPackage group into a Process chain?
Yes, Double Click on the info package grp → Process Chain Maintenance button and type in the name and description.
72) When you define aggregates, what are the available options?
F fixed value
73) Can you setup InfoObjects as Virtual Providers?
74) To perform a Union operation on InfoProviders, which InfoProvider is uses?
75)Explain the different between Operation Data store, InfoCube and MultiProvider?
They provide granular data, allows overwrite and data is in transparent tables, ideal for drilldown and RRI.
This is used for star schema, we can only append data, ideal for primary reporting.
It contains a physical data and allow to access data from different InfoProviders.
76) What do you understand by Start and update routine?
Start Routines − The start routine is run for each Data Package after the data has been written to the PSA and before the transfer rules have been executed. It allows complex computations for a key figure or a characteristic. It has no return value. Its purpose is to execute preliminary calculations and to store them in global Data Structures
77) Mention what are the maximum number of dimensions in info cubes?
In info cubes, there are 16 dimensions ( 3 sap defined and 1 customer defined)
78) What is the dimension in BW? How would you optimize the dimensions?
A dimension in BW is a collection of reference information about a measurable event in data warehousing. In this context, events are known as “facts”. For example, a customer dimension’s attributes could include first and last name, gender, birth date etc. To optimize the dimensions, do not add most dynamic characteristics into the same dimension and make the dimension smaller. Also, define as many dimensions as possible, and the dimension should not exceed 20% of the fact table size.
79) What are info objects?
Characteristics and key figures will be called as info objects. ‘Info-objects’ are similar to fields of the source system, data based on which we organize data in different info provider in BW.
80)What is an InfoObject and why it is used in SAP BI?
Info Objects are known as smallest unit in SAP BI and are used in Info Providers, DSOs, Multi providers, etc. Each Info Provider contains multiple Info Objects.
InfoObjects are used in reports to analyze the data stored and to provide information to decision makers.
81) What is the content of a fact table?
a) The key figures for a combination of characteristic SID values of the dimensions are stored in the fact table.
b) Changes to master data tables are only possible if new dimension keys are created in the fact table.
c) Both cumulative values and also key figures for non-cumulative values can be contained in the fact table.
82) What are the BEx Broadcaster and external sources of data?
a) You can broadcast external, non – SAP data sources directly as long as they are read through the staging BAPI.
b) The external data sources must be multi-dimensional sources.
c) The external data sources must be mapped through a VirtualProvider.
d) External data sources are read through the Java connectors XMLA or ODBO.
Data integrity is to eliminate duplicate entries in the database.
83) What is data flow in BW/BI?
Data flows from a transactional system to the analytical system (BW). DS ( Data Service) on the transactional system needs to be replicated on BW side and attached to infosource and update rules respectively.
84) What is an ‘Infocube’?
‘Infocube’ is structured as the star schema and it is a data storage area. To create an infocube, you require 1 ‘fact table’ surrounded by 4 dimensions. The ‘fact table’ is surrounded by different dim table, which are linked with DIM’ ids. And as per the data, you will have aggregated data in the cubes.
85)How many tables does info cube contain?
Info cubes contain two tables, Fact table and Dimensions table.