Informatica Interview Questionnaire

Informatica Interview Questionnaire

1.       What are the components of Informatica? And what is the purpose of each?

Ans:  Informatica Designer, Server Manager & Repository Manager. Designer for Creating Source & Target definitions, Creating Mapplets and Mappings etc. Server Manager for creating sessions & batches, Scheduling the sessions & batches, Monitoring the triggered sessions and batches, giving post and pre session commands, creating database connections to various instances etc. Repository Manage for Creating and Adding repositories, Creating & editing folders within a repository, Establishing users, groups, privileges & folder permissions, Copy, delete, backup a repository, Viewing the history of sessions, Viewing the locks on various objects and removing those locks etc.

2.       What is a repository? And how to add it in an informatica client?

Ans: It’s a location where all the mappings and sessions related information is stored. Basically it’s a database where the metadata resides. We can add a repository through the Repository manager.

3.       Name at least 5 different types of transformations used in mapping design and state the use of each.

Ans: Source Qualifier – Source Qualifier represents all data queries from the source, Expression – Expression performs simple calculations,

Filter – Filter serves as a conditional filter,

Lookup – Lookup looks up values and passes to other objects,

Aggregator  - Aggregator performs aggregate calculations.

4.       How can a transformation be made reusable?

Ans: In the edit properties of any transformation there is a check box to make it reusable, by checking that it becomes reusable. You can even create reusable transformations in Transformation developer.

5.       How are the sources and targets definitions imported in informatica designer? How to create Target definition for flat files?

Ans: When you are in source analyzer there is a option in main menu to Import the source from Database, Flat File, Cobol File & XML file, by selecting any one of them you can import a source definition. When you are in Warehouse Designer there is an option in main menu to import the target from Database, XML from File and XML from sources you can select any one of these.

There is no way to import target definition as file in Informatica designer. So while creating the target definition for a file in the warehouse designer it is created considering it as a table, and then in the session properties of that mapping it is specified as file.

6.       Explain what is sql override for a source table in a mapping.

Ans: The Source Qualifier provides the SQL Query option to override the default query. You can enter any SQL statement supported by your source database. You might enter your own SELECT statement, or have the database perform aggregate calculations, or call a stored procedure or stored function to read the data and perform some tasks.

7.       What is lookup override?

Ans: This feature is similar to entering a custom query in a Source Qualifier transformation. When entering a Lookup SQL Override, you can enter the entire override, or generate and edit the default SQL statement.

The lookup query override can include WHERE clause.

8.       What are mapplets? How is it different from a Reusable Transformation?

Ans: A mapplet is a reusable object that represents a set of transformations. It allows you to reuse transformation logic and can contain as many transformations as you need. You create mapplets in the Mapplet Designer.

Its different than a reusable transformation as it may contain a set of transformations, while a reusable transformation is a single one.

9.       How to use an oracle sequence generator in a mapping?

Ans: We have to write a stored procedure, which can take the sequence name as input and dynamically generates a nextval from that sequence. Then in the mapping we can use that stored procedure through a procedure transformation.

10.    What is a session and how to create it?

Ans: A session is a set of instructions that tells the Informatica Server how and when to move data from sources to targets. You create and maintain sessions in the Server Manager.

11.    How to create the source and target database connections in server manager?

Ans: In the main menu of server manager there is menu “Server Configuration”, in that there is the menu “Database connections”. From here you can create the Source and Target database connections.

12.    Where are the source flat files kept before running the session?

Ans: The source flat files can be kept in some folder on the Informatica server or any other machine, which is in its domain.

13.    What are the oracle DML commands possible through an update strategy?

Ans: dd_insert, dd_update, dd_delete & dd_reject.

14.    How to update or delete the rows in a target, which do not have key fields?

Ans: To Update a table that does not have any Keys we can do a SQL Override of the Target Transformation by specifying the WHERE conditions explicitly.  Delete cannot be done this way. In this case you have to specifically mention the Key for Target table definition on the Target transformation in the Warehouse Designer and    delete the row using the Update Strategy transformation.

15.    What is option by which we can run all the sessions in a batch simultaneously?

Ans: In the batch edit box there is an option called concurrent. By checking that all the sessions in that Batch will run concurrently.

16.    Informatica settings are available in which file?

Ans: Informatica settings are available in a file pmdesign.ini   in Windows folder.

17.    How can we join the records from two heterogeneous sources in a mapping?

Ans: By using a joiner.

18.    Difference between Connected & Unconnected look-up.

Ans: An unconnected Lookup transformation exists separate from the pipeline in the mapping. You write an expression using the :LKP reference qualifier to call the lookup within another transformation. While the connected lookup forms a part of the whole flow of mapping.

19.    Difference between Lookup Transformation & Unconnected Stored Procedure Transformation – Which one is faster ?

20.    Compare Router Vs Filter & Source Qualifier Vs Joiner.

Ans: A Router transformation has input ports and output ports. Input ports reside in the input group, and output ports reside in the output groups. Here you can test data based on one or more group filter conditions.

But in filter you can filter data based on one or more conditions before writing it to targets.

A source qualifier can join data coming from same source database. While a joiner is used to combine data from heterogeneous sources. It can even join data from two tables from same database.

A source qualifier can join more than two sources. But a joiner can join only two sources.

21.    How to Join 2 tables connected to a Source Qualifier w/o having any relationship defined ?

Ans: By writing an sql override.

22.    In a mapping there are 2 targets to load header and detail, how to ensure that header loads first then detail table.

Ans: Constraint Based Loading (if no relationship at oracle level) OR Target Load Plan (if only 1 source qualifier for both tables) OR select first the header target table and then the detail table while dragging them in mapping.

23.    A mapping just take 10 seconds to run, it takes a source file and insert into target, but before that there is a Stored Procedure transformation which takes around 5 minutes to run and gives output ‘Y’ or ‘N’. If Y then continue feed or else stop the feed. (Hint: since SP transformation takes more time compared to the mapping, it shouldn’t run row wise).

Ans: There is an option to run the stored procedure before starting to load the rows.

Data warehousing concepts

1.What is difference between view and materialized view?

Views contains query whenever execute views it has read from base table

Where as M views loading or replicated takes place only once, which gives you better query performance

Refresh m views 1.on commit and 2. on demand

(Complete, never, fast, force)

2.What is bitmap index why it’s used for DWH?

A bitmap for each key value replaces a list of rowids. Bitmap index more efficient for data warehousing because low cardinality, low updates, very efficient for where class

3.What is star schema? And what is snowflake schema?

The center of the star consists of a large fact table and the points of the star are the dimension tables.

Snowflake schemas normalized dimension tables to eliminate redundancy. That is, the

Dimension data has been grouped into multiple tables instead of one large table.

Star schema contains demoralized dimension tables and fact table, each primary key values in dimension table associated with foreign key of fact tables.

Here a fact table contains all business measures (normally numeric data) and foreign key values, and dimension tables has details about the subject area.

Snowflake schema basically a normalized dimension tables to reduce redundancy in the dimension tables

4.Why need staging area database for DWH?

Staging area needs to clean operational data before loading into data warehouse.

Cleaning in the sense your merging data which comes from different source

5.What are the steps to create a database in manually?

create os service and create init file and start data base no mount stage then give create data base command.

6.Difference between OLTP and DWH?

OLTP system is basically application orientation (eg, purchase order it is functionality of an application)

Where as in DWH concern is subject orient (subject in the sense custorer, product, item, time)

OLTP

·       Application Oriented

·       Used to run business

·       Detailed data

·       Current up to date

·       Isolated Data

·       Repetitive access

·       Clerical User

·       Performance Sensitive

·       Few Records accessed at a time (tens)

·       Read/Update Access

·       No data redundancy

·       Database Size 100MB-100 GB

DWH

·       Subject Oriented

·       Used to analyze business

·       Summarized and refined

·       Snapshot data

·       Integrated Data

·       Ad-hoc access

·       Knowledge User

·       Performance relaxed

·       Large volumes accessed at a time(millions)

·       Mostly Read (Batch Update)

·       Redundancy present

·       Database Size 100 GB - few terabytes

7.Why need data warehouse?

A single, complete and consistent store of data obtained from a variety of different sources made available to end users in a what they can understand and use in a business context.

A process of transforming data into information and making it available to users in a timely enough manner to make a difference Information

Technique for assembling and managing data from various sources for the purpose of answering business questions. Thus making decisions that were not previous possible

8.What is difference between data mart and data warehouse?

A data mart designed for a particular line of business, such as sales, marketing, or finance.

Where as data warehouse is enterprise-wide/organizational

The data flow of data warehouse depending on the approach

9.What is the significance of surrogate key?

Surrogate key used in slowly changing dimension table to track old and new values and it’s derived from primary key.

 

10.What is slowly changing dimension. What kind of scd used in your project?

Dimension attribute values may change constantly over the time. (Say for example customer dimension has customer_id,name, and address) customer address may change over time.

How will you handle this situation?

There are 3 types, one is we can overwrite the existing record, second one is create additional new record at the time of change with the new attribute values.

Third one is create new field to keep new values in the original dimension table.

11.What is difference between primary key and unique key constraints?

Primary key maintains uniqueness and not null values

Where as unique constrains maintain unique values and null values

12.What are the types of index? And is the type of index used in your project?

Bitmap index, B-tree index, Function based index, reverse key and composite index.

We used Bitmap index in our project for better performance.

13.How is your DWH data modeling(Details about star schema)?

14.A table have 3 partitions but I want to update in 3rd partitions how will you do?

Specify partition name in the update statement. Say for example

Update employee partition(name) a, set a.empno=10 where ename=’Ashok’

15.When you give an update statement how memory flow will happen and how oracles allocate memory for that?

Oracle first checks in Shared sql area whether same Sql statement is available if it is there it uses. Otherwise allocate memory in shared sql area and then create run time memory in Private sql area to create parse tree and execution plan. Once it completed stored in the shared sql area wherein previously allocated memory

16.Write a query to find out 5th max salary? In Oracle, DB2, SQL Server

Select (list the columns you want) from (select salary from employee order by salary)

Where rownum<5

17.When you give an update statement how undo/rollback segment will work/what are the steps?

Oracle keep old values in undo segment and new values in redo entries. When you say rollback it replace old values from undo segment. When you say commit erase the undo segment values and keep new vales in permanent.

Informatica Administration

18.What is DTM? How will you configure it?

DTM transform data received from reader buffer and its moves transformation to transformation on row by row basis and it uses transformation caches when necessary.

19.You transfer 100000 rows to target but some rows get discard how will you trace them? And where its get loaded?

Rejected records are loaded into bad files. It has record indicator and column indicator.

Record indicator identified by (0-insert,1-update,2-delete,3-reject) and column indicator identified by (D-valid,O-overflow,N-null,T-truncated).

Normally data may get rejected in different reason due to transformation logic

20.What are the different uses of a repository manager?

Repository manager used to create repository which contains metadata the informatica uses to transform data from source to target. And also it use to create informatica user’s and folders and copy, backup and restore the repository

21.How do you take care of security using a repository manager?

Using repository privileges, folder permission and locking.

Repository privileges(Session operator, Use designer, Browse repository, Create session and batches, Administer repository, administer server, super user)

Folder permission(owner, groups, users)

Locking(Read, Write, Execute, Fetch, Save)

22.What is a folder?

Folder contains repository objects such as sources, targets, mappings, transformation which are helps logically organize our data warehouse.

23.Can you create a folder within designer?

Not possible

24.What are shortcuts? Where it can be used? What are the advantages?

There are 2 shortcuts(Local and global) Local used in local repository and global used in global repository. The advantage is reuse an object without creating multiple objects. Say for example a source definition want to use in 10 mappings in 10 different folder without creating 10 multiple source you create 10 shotcuts.

25.How do you increase the performance of mappings?

Use single pass read(use one source qualifier instead of multiple SQ for same table)

Minimize data type conversion (Integer to Decimal again back to Integer)

Optimize transformation(when you use Lookup, aggregator, filter, rank and joiner)

Use caches for lookup

Aggregator use presorted port, increase cache size, minimize input/out port as much as possible

Use Filter wherever possible to avoid unnecessary data flow

26.Explain Informatica Architecture?

Informatica consist of client and server. Client tools such as Repository manager, Designer, Server manager. Repository data base contains metadata it read by informatica server used read data from source, transforming and loading into target.

27.How will you do sessions partitions?

It’s not available in power part 4.7

Transformation

28.What are the constants used in update strategy?

DD_INSERT, DD_UPDATE, DD_DELETE, DD_REJECT

29.What is difference between connected and unconnected lookup transformation?

Connected lookup return multiple values to other transformation

Where as unconnected lookup return one values

If lookup condition matches Connected lookup return user defined default values

Where as unconnected lookup return null values

Connected supports dynamic caches where as unconnected supports static

30.What you will do in session level for update strategy transformation?

In session property sheet set Treat rows as “Data Driven”

31.What are the port available for update strategy , sequence generator,  Lookup, stored procedure transformation?

Transformations                          Port

Update strategy                                           Input, Output

Sequence Generator                  Output only

Lookup                                                          Input, Output, Lookup, Return

Stored Procedure                        Input, Output

32.Why did you used connected stored procedure why don’t use unconnected stored procedure?

33.What is active and passive transformations?

Active transformation change the no. of records when passing to targe(example filter)

where as passive transformation will not change the transformation(example expression)

34.What are the tracing level?

Normal – It contains only session initialization details and transformation details no. records rejected, applied

Terse -  Only initialization details will be there

Verbose Initialization – Normal setting information plus detailed information about the transformation.

Verbose data – Verbose init. Settings and all information about the session

 

35.How will you make records in groups?

Using group by port in aggregator

36.Need to store value like 145 into target when you use aggregator, how will you do that?

Use Round() function

37.How will you move mappings from development to production database?

Copy all the mapping from development repository and paste production repository while paste it will promt whether you want replace/rename. If say replace informatica replace all the source tables with repository database.

38.What is difference between aggregator and expression?

Aggregator is active transformation and expression is passive transformation

Aggregator transformation used to perform aggregate calculation on group of records   really

Where as expression used perform calculation with single record

39.Can you use mapping without source qualifier?

Not possible, If source RDBMS/DBMS/Flat file use SQ or use normalizer if the source cobol feed

40.When do you use a normalizer?

Normalized can be used in Relational to denormilize data.

41.What are stored procedure transformations. Purpose of sp transformation. How did you go about using your project?

Connected and unconnected stored procudure.

Unconnected stored procedure used for data base level activities such as pre and post load

Connected stored procedure used in informatica level  for example passing one parameter as input and capturing return value from the stored procedure.

Normal   - row wise check

Pre-Load Source  - (Capture source incremental data for incremental aggregation)

Post-Load Source - (Delete Temporary tables)

Pre-Load Target - (Check disk space available)

Post-Load Target – (Drop and recreate index)

42.What is lookup and difference between types of lookup. What exactly happens when a lookup is cached. How does a dynamic lookup cache work.

Lookup transformation used for check values in the source and target tables(primary key values).

There are 2 type connected and unconnected transformation

Connected lookup returns multiple values if condition true

Where as unconnected return a single values through return port.

Connected lookup return default user value if the condition does not mach

Where as unconnected return null values

Lookup cache does:

Read the source/target table and stored in the lookup cache

43.What is a joiner transformation?

Used for heterogeneous sources(A relational source and a flat file)

Type of joins:

Assume 2 tables has values(Master - 1, 2, 3 and Detail - 1, 3, 4)

Normal(If the condition mach both master and detail tables then the records will be displaced. Result set 1, 3)

Master Outer(It takes all the rows from detail table and maching rows from master table. Result set 1, 3, 4)

Detail Outer(It takes all the values from master source and maching values from detail table. Result set 1, 2, 3)

Full Outer(It takes all values from both tables)

44.What is aggregator transformation how will you use in your project?

Used perform aggregate calculation on group of records and we can use conditional clause to filter data

45.Can you use one mapping to populate two tables in different schemas?

Yes we can use

46.Explain lookup cache, various caches?

Lookup transformation used for check values in the source and target tables(primary key values).

Various Caches:

Persistent cache (we can save the lookup cache files and reuse them the next time process the lookup transformation)

Re-cache from database (If the persistent cache not synchronized with lookup table you can configure the lookup transformation to rebuild the lookup cache)

Static cache (When the lookup condition is true, Informatica server return a value from lookup cache and it’s does not update the cache while it processes the lookup transformation)

Dynamic cache (Informatica server dynamically inserts new rows or update existing rows in the cache and the target. Suppose if we want lookup a target table we can use dynamic cache)

Shared cache (we can share lookup transformation between multiple transformations in a mapping. 2 lookup in a mapping can share single lookup cache)

47.Which path will the cache be created?

User  specified directory. If we say c:\  all the cache files created in this directory.

48.Where do you specify all the parameters for lookup caches?

Lookup property sheet/tab.

49.How do you remove the cache files after the transformation?

After session complete, DTM remove cache memory and deletes caches files.

In case using persistent cache and Incremental aggregation then caches files will be saved.

50.What is the use of aggregator transformation?

To perform Aggregate calculation

Use conditional clause to filter data in the expression Sum(commission, Commission >2000)

Use non-aggregate function iif (max(quantity) > 0, Max(quantitiy), 0))

51.What are the contents of index and cache files?

Index caches files hold unique group values as determined by group by port in the transformation.

Data caches files hold row data  until it performs necessary calculation.

52.How do you call a store procedure within a transformation?

In the expression transformation create new out port in the expression write :sp.stored procedure name(arguments)

53.Is there any performance issue in connected & unconnected lookup? If yes, How?

Yes

Unconnected lookup much more faster than connected lookup why because in unconnected not connected to any other transformation we are calling it from other transformation so it minimize lookup cache value

Where as connected transformation connected to other transformation so it keeps values in the lookup cache.

54.What is dynamic lookup?

When we use target lookup table, Informatica server dynamically insert new values or it updates if the values exist and passes to target table.

55.How Informatica read data if source have one relational and flat file?

Use joiner transformation after source qualifier before other transformation.

56.How you will load unique record into target flat file from source flat files has duplicate data?

There are 2 we can do this either we can use Rank transformation or oracle external table

In rank transformation using group by port (Group the records) and then set no. of rank 1. Rank transformation return one value from the group. That the values will be a unique one.

57.Can you use flat file for repository?

No, We cant

58.Can you use flat file for lookup table?

No, We cant

59.Without Source Qualifier and joiner how will you join tables?

In session level we have option user defined join. Where we can write join condition.

60.Update strategy set DD_Update but in session level have insert. What will happens?

Insert take place. Because this option override the mapping level option

Sessions and batches

61.What are the commit intervals?

Source based commit (Based on the no. of active source records(Source qualifier) reads. Commit interval set 10000 rows and source qualifier reads 10000 but due to transformation logic 3000 rows get rejected when 7000 reach target commit will fire, so writer buffer does not rows held the buffer)

Target based commit (Based on the rows in the buffer and commit interval. Target based commit set 10000 but writer buffer fills every 7500, next time buffer fills 15000 now commit statement will fire then 22500 like go on.)

62.When we use router transformation?

When we want perform multiple condition to filter out data then we go for router. (Say for example source records 50 filter condition mach 10 records remaining 40 records get filter out but still we want perform few more filter condition to filter remaining 40 records.)

63.How did you schedule sessions in your project?

Run once (set 2 parameter date and time when session should start)

Run Every (Informatica server run session at regular interval as we configured, parameter Days, hour, minutes, end on, end after, forever)

Customized repeat (Repeat every 2 days, daily frequency hr, min, every week, every month)

Run only on demand(Manually run) this not session scheduling.

64.How do you use the pre-sessions and post-sessions in sessions wizard, what for they used?

Post-session used for email option when the session success/failure send email. For that we should configure

Step1. Should have a informatica startup account and create outlook profile for that user

Step2. Configure Microsoft exchange server in mail box applet(control panel)

Step3. Configure informatica server miscellaneous tab have one option called MS exchange profile where we have specify the outlook profile name.

Pre-session used for even scheduling (Say for example we don’t know whether source file available or not in particular directory. For that we write one DOS command to move file directory to destination and set event based scheduling option in session property sheet Indicator file wait for).

65.What are different types of batches. What are the advantages and dis-advantages of a concurrent batch?

Sequential(Run the sessions one by one)

Concurrent (Run the sessions simultaneously)

Advantage of concurrent batch:

It’s takes informatica server resource and reduce time it takes run session separately.

Use this feature when we have multiple sources that process large amount of data in one session. Split sessions and put into one concurrent batches to complete quickly.

Disadvantage

Require more shared memory otherwise session may get failed

66.How do you handle a session if some of the records fail. How do you stop the session in case of errors. Can it be achieved in mapping level or session level?

It can be achieved in session level only. In session property sheet, log files tab one option is the error handling Stop on ------ errors. Based on the error we set informatica server stop the session.

67.How you do improve the performance of session.

If we use Aggregator transformation use sorted port, Increase aggregate cache size, Use filter before aggregation so that it minimize unnecessary aggregation.

Lookup transformation use lookup caches

Increase DTM shared memory allocation

Eliminating transformation errors using lower tracing level(Say for example a mapping has 50 transformation when transformation error occur informatica server has to write in session log file it affect session performance)

68.Explain incremental aggregation. Will that increase the performance? How?

Incremental aggregation capture whatever changes made in source used for aggregate calculation in a session, rather than processing the entire source and recalculating the same calculation each time session run. Therefore it improve session performance.

Only use incremental aggregation following situation:

Mapping have aggregate calculation

Source table changes incrementally

Filtering source incremental data by time stamp

Before Aggregation have to do following steps:

Use filter transformation to remove pre-existing records

Reinitialize aggregate cache when source table completely changes for example incremental changes happing daily and complete changes happenings monthly once. So when the source table completely change we have reinitialize the aggregate cache and truncate target table use new source table. Choose Reinitialize cache in the aggregation behavior in transformation tab

69.Concurrent batches have 3 sessions and set each session run if previous complete but 2nd fail then what will happen the batch?

Batch will fail

General Project

70. How many mapping, dimension tables, Fact tables and any complex mapping you did? And what is your database size, how frequently loading to DWH?

I did 22 Mapping, 4 dimension table and one fact table. One complex mapping I did for slowly changing dimension table. Database size is 9GB. Loading data every day

71. What are the different transformations used in your project?

Aggregator, Expression, Filter, Sequence generator, Update Strategy, Lookup, Stored Procedure, Joiner, Rank, Source Qualifier.

72. How did you populate the dimensions tables?

73. What are the sources you worked on?

Oracle

74. How many mappings have you developed on your whole dwh project?

45 mappings

75. What is OS used your project?

Windows NT

76. Explain your project (Fact table, dimensions, and database size)

Fact table contains all business measures (numeric values) and foreign key values, Dimension table contains details about subject area like customer, product

77.What is difference between Informatica power mart and power center?

Using power center we can create global repository

Power mart used to create local repository

Global repository configure multiple server to balance session load

Local repository configure only single server

78.Have you done any complex mapping?

Developed one mapping to handle slowly changing dimension table.

79.Explain details about DTM?

Once we session start, load manager start DTM and it allocate session shared memory and contains reader and writer. Reader will read source data from source qualifier using SQL statement and move data to DTM then DTM transform data to transformation to transformation and row by row basis finally move data to writer then writer write data into target using SQL statement.

I-Flex Interview (14^th May 2003)

80.What are the key you used other than primary key and foreign key?

 

Used surrogate key to maintain uniqueness to overcome duplicate value in the primary key.

81.Data flow of your Data warehouse(Architecture)

DWH is a basic architecture (OLTP to Data warehouse from DWH OLAP analytical and report building.

82.Difference between Power part and power center?

Using power center we can create global repository

Power mart used to create local repository

Global repository configure multiple server to balance session load

Local repository configure only single server

83.What are the batches and it’s details?

Sequential(Run the sessions one by one)

Concurrent (Run the sessions simultaneously)

Advantage of concurrent batch:

It’s takes informatica server resource and reduce time it takes run session separately.

Use this feature when we have multiple sources that process large amount of data in one session. Split sessions and put into one concurrent batches to complete quickly.

Disadvantage

Require more shared memory otherwise session may get failed

84.What is external table in oracle. How oracle read the flat file

Used for read flat file. Oracle internally write SQL loader script with control file.

85.What are the index you used? Bitmap join index?

Bitmap index used in data warehouse environment to increase query response time, since DWH has low cardinality, low updates, very efficient for where clause.

Bitmap join index used to join dimension and fact table instead reading 2 different index.

86.What are the partitions in 8i/9i? Where you will use hash partition?

In oracle8i there are 3 partition (Range, Hash, Composite)

In Oracle9i List partition is additional one

Range (Used for Dates values for example in DWH ( Date values are Quarter 1, Quarter 2, Quarter 3, Quater4)

Hash (Used for unpredictable values say for example we cant able predict which value to allocate which partition then we go for hash partition. If we set partition 5 for a column oracle allocate values into 5 partition accordingly).

List (Used for literal values say for example a country have 24 states create 24 partition for 24 states each)

Composite (Combination of range and hash)

91.What is main difference mapplets and mapping?

Reuse the transformation in several mappings, where as mapping not like that.

If any changes made in mapplets it automatically inherited in all other instance mapplets.

92. What is difference between the source qualifier filter and filter transformation?

Source qualifier filter only used for relation source where as Filter used any kind of source.

Source qualifier filter data while reading where as filter before loading into target.

93. What is the maximum no. of return value when we use unconnected

transformation?

Only one.

94. What are the environments in which informatica server can run on?

Informatica client runs on Windows 95 / 98 / NT, Unix Solaris, Unix AIX(IBM)

Informatica Server runs on Windows NT / Unix

Minimum Hardware requirements

Informatica Client Hard disk 40MB, RAM 64MB

Informatica Server Hard Disk 60MB, RAM 64MB

95. Can unconnected lookup do everything a connected lookup transformation can do?

No, We cant call connected lookup in other transformation. Rest of things it’s possible

96. In 5.x can we copy part of mapping and paste it in other mapping?

I think its possible

97. What option do you select for a sessions in batch, so that the sessions run one

after the other?

We have select an option called “Run if previous completed”

98.    How do you really know that paging to disk is happening while you are using a lookup transformation? Assume you have access to server?

We have collect performance data first then see the counters parameter lookup_readtodisk if it’s greater than 0 then it’s read from disk

Step1. Choose the option “Collect Performance data” in the general tab session property

            sheet.

Step2. Monitor server then click server-request à session performance details

Step3. Locate the performance details file named called session_name.perf file in the session

           log file directory

Step4. Find out counter parameter lookup_readtodisk if it’s greater than 0 then informatica

           read lookup table values from the disk. Find out how many rows in the cache see

           Lookup_rowsincache

99.    List three option available in informatica to tune aggregator transformation?

Use Sorted Input to sort data before aggregation

Use Filter transformation before aggregator

Increase Aggregator cache size

100.Assume there is text file as source having a binary field to, to source qualifier What native data type informatica will convert this binary field to in source qualifier?

Binary data type for relational source  for flat file ?

101.Variable v1 has values set as 5 in designer(default), 10 in parameter file, 15 in

       repository. While running session which value informatica will read?

Informatica read value 15 from repository

102. Joiner transformation is joining two tables s1 and s2. s1 has 10,000 rows and s2 has 1000 rows . Which table you will set master for better performance of joiner

transformation? Why?

Set table S2 as Master table because informatica server has to keep master table in the cache so if it is 1000 in cache will get performance instead of having 10000 rows in cache

103. Source table has 5 rows. Rank in rank transformation is set to 10. How many rows the rank transformation will output?

5 Rank

104. How to capture performance statistics of individual transformation in the mapping and explain some important statistics that can be captured?

Use tracing level Verbose data

105. Give a way in which you can implement a real time scenario where  data in a table is changing and you need to look up data from it. How will you configure the lookup transformation for this purpose?

In slowly changing dimension table use type 2 and model 1

106. What is DTM process? How many threads it creates to process data, explain each

thread in brief?

DTM receive data from reader and move data to transformation to transformation on row by row basis. It’s create 2 thread one is reader and another one is writer

107. Suppose session is configured with commit interval of 10,000 rows and source has 50,000 rows explain the commit points for source based commit & target based commit. Assume appropriate value wherever required?

Target Based commit (First time Buffer size full 7500 next time 15000)

Commit Every 15000, 22500, 30000, 40000, 50000

Source Based commit(Does not affect rows held in buffer)

Commit Every 10000, 20000, 30000, 40000, 50000

108.What does first column of bad file (rejected rows) indicates?

First Column - Row indicator (0, 1, 2, 3)

Second Column – Column Indicator (D, O, N, T)

109. What is the formula for calculation rank data caches? And also Aggregator, data, index caches?

Index cache size = Total no. of rows * size of the column in the lookup condition (50 * 4)

Aggregator/Rank transformation Data Cache size = (Total no. of rows * size of the column in the lookup condition) + (Total no. of rows * size of the connected output ports)

110. Can unconnected lookup return more than 1 value? No

INFORMATICA TRANSFORMATIONS

·          Aggregator

·          Expression

·          External Procedure

·          Advanced External Procedure

·          Filter

·          Joiner

·          Lookup

·          Normalizer

·          Rank

·          Router

·          Sequence Generator

·          Stored Procedure

·          Source Qualifier

·          Update Strategy

·          XML source qualifier

Expression Transformation

-                      You can use ET to calculate values in a single row before you write to the target

-                      You can use ET, to perform any non-aggregate calculation

-                      To perform calculations involving multiple rows, such as sums of averages, use the Aggregator. Unlike ET the Aggregator Transformation allow you to group and sort data

Calculation

To use the Expression Transformation to calculate values for a single row, you must include the following ports.

-                      Input port for each value used in the calculation

-                      Output port for the expression

NOTE

You can enter multiple expressions in a single ET. As long as you enter only one expression for each port, you can create any number of  output ports in the Expression Transformation. In this way, you can use one expression transformation rather than creating separate transformations for each calculation that requires the same set of data.

Sequence Generator Transformation

-                      Create keys

-                      Replace missing values

-                      This contains two output ports that you can connect to one or more transformations. The server generates a value each time a row enters a connected transformation, even if that value is not used.

-                      There are two parameters NEXTVAL, CURRVAL

-                      The SGT can be reusable

-                      You can not edit any default ports (NEXTVAL, CURRVAL)

SGT Properties

-                      Start value

-                      Increment By

-                      End value

-                      Current value

-                      Cycle              (If selected, server cycles through sequence range. Otherwise,        

                                Stops with configured end value)

-                      Reset

-                      No of cached values

NOTE

-                      Reset is disabled for Reusable SGT

-                      Unlike other transformations, you cannot override SGT properties at session level. This protects the integrity of sequence values generated.

Aggregator Transformation

Difference between Aggregator and Expression Transformation

                We can use Aggregator to perform calculations on groups. Where as the Expression transformation permits you to calculations on row-by-row basis only.

The server performs aggregate calculations as it  reads and stores necessary data group and row data in an aggregator cache.

When Incremental aggregation occurs, the server passes new source data through the mapping and uses historical cache data to perform new calculation incrementally.

Components

-                      Aggregate Expression

-                      Group by port

-                      Aggregate cache

When a session is being run using aggregator transformation, the server creates Index and data caches in memory to process the transformation. If the server requires more space, it stores overflow values in cache files.

NOTE

The performance of aggregator transformation can be improved by using “Sorted Input option”. When this is selected, the server assumes all data is sorted by group.

Incremental Aggregation

-                      Using this, you apply captured changes in the source to aggregate calculation in a session. If the source changes only incrementally and you can capture changes, you can configure the session to process only those changes

-                      This allows the sever to update the target incrementally, rather than forcing it to process the entire source and recalculate the same calculations each time you run the session.

Steps:

-                      The first time you run a session with incremental aggregation enabled, the server process the entire source.

-                      At the end of the session, the server stores aggregate data from that session ran in two files, the index file and data file. The server creates the file in local directory.

-                      The second time you run the session, use only changes in the source as source data for the session. The server then performs the following actions:

(1)                 For  each input record, the session checks the historical information in the index file for a corresponding group, then:

If it finds a corresponding group –

The server performs the aggregate operation incrementally, using the aggregate data for that group, and saves the incremental changes.

Else

                Server create a new group and saves the record data