Saturday, August 18, 2012
Unix interview questions
Email variable - %a (attach the file) %g – attach session log file
How do identify the empty line in a flat file in Unix? How to remove it?
grep –v “^$” filename
List the files in ascending order in Unix?
ls -lt (sort by last date modified) ls –ltr (reverse)
ls –lS (sort by size of the file)
How to open a Database using Unix Command
mysql -u uname -h hostname –p pwd
What is command to check space in Unix?
Ans: df -k
What is command to kill last background Job?
Ans: kill $!
How you will list all Hidden files?
Ans: ls -la|grep ^[.]
How to kill a process forcibly?
Ans: kill -9 PID (Process Identification Number)
How to print/display the first line of a file?
There are many ways to do this. However the easiest way to display the first line of a file is using the [head] command.
$> head -1 file.txt
No prize in guessing that if you specify [head -2] then it would print first 2 records of the file.
Another
way can be by using [sed] command. [Sed] is a very powerful text editor
which can be used for various text manipulation purposes like this.
$> sed '2,$ d' file.txt
How
does the above command work? The 'd' parameter basically tells [sed] to
delete all the records from display from line 2 to last line of the
file (last line is represented by $ symbol). Of course it does not
actually delete those lines from the file, it just does not display
those lines in standard output screen. So you only see the remaining
line which is the 1st line.
How to print/display the last line of a file?
The easiest way is to use the [tail] command.
$> tail -1 file.txt
If you want to do it using [sed] command, here is what you should write:
$> sed -n '$ p' test
From
our previous answer, we already know that '$' stands for the last line
of the file. So '$ p' basically prints (p for print) the last line in
standard output screen. '-n' switch takes [sed] to silent mode so that
[sed] does not print anything else in the output.
How to display n-th line of a file?
The
easiest way to do it will be by using [sed] I guess. Based on what we
already know about [sed] from our previous examples, we can quickly
deduce this command:
$> sed –n '<n> p' file.txt
You need to replace <n> with the actual line number. So if you want to print the 4th line, the command will be
$> sed –n '4 p' test
Of course you can do it by using [head] and [tail] command as well like below:
$> head -<n> file.txt | tail -1
You need to replace <n> with the actual line number. So if you want to print the 4th line, the command will be
$> head -4 file.txt | tail -1
How to remove the first line / header from a file?
We
already know how [sed] can be used to delete a certain line from the
output – by using the'd' switch. So if we want to delete the first line
the command should be:
$> sed '1 d' file.txt
But
the issue with the above command is, it just prints out all the lines
except the first line of the file on the standard output. It does not
really change the file in-place. So if you want to delete the first line
from the file itself, you have two options.
Either you can redirect the output of the file to some other file and then rename it back to original file like below:
$> sed '1 d' file.txt > new_file.txt
$> mv new_file.txt file.txt
Or, you can use an inbuilt [sed] switch '–i' which changes the file in-place. See below:
$> sed –i '1 d' file.txt
How to remove the last line/ trailer from a file in Unix script?
Always remember that [sed] switch '$' refers to the last line. So using this knowledge we can deduce the below command:
$> sed –i '$ d' file.txt
How to remove certain lines from a file in Unix?
If
you want to remove line <m> to line <n> from a given file,
you can accomplish the task in the similar method shown above. Here is
an example:
$> sed –i '5,7 d' file.txt
The above command will delete line 5 to line 7 from the file file.txt
How to remove the last n-th line from a file?
This
is bit tricky. Suppose your file contains 100 lines and you want to
remove the last 5 lines. Now if you know how many lines are there in the
file, then you can simply use the above shown method and can remove all
the lines from 96 to 100 like below:
$> sed –i '96,100 d' file.txt # alternative to command [head -95 file.txt]
But
not always you will know the number of lines present in the file (the
file may be generated dynamically, etc.) In that case there are many
different ways to solve the problem. There are some ways which are quite
complex and fancy. But let's first do it in a way that we can
understand easily and remember easily. Here is how it goes:
$> tt=`wc -l file.txt | cut -f1 -d' '`;sed –i "`expr $tt - 4`,$tt d" test
As
you can see there are two commands. The first one (before the
semi-colon) calculates the total number of lines present in the file and
stores it in a variable called “tt”. The second command (after the
semi-colon), uses the variable and works in the exact way as shows in
the previous example.
How to check the length of any line in a file?
We already know how to print one line from a file which is this:
$> sed –n '<n> p' file.txt
Where
<n> is to be replaced by the actual line number that you want to
print. Now once you know it, it is easy to print out the length of this
line by using [wc] command with '-c' switch.
$> sed –n '35 p' file.txt | wc –c
The above command will print the length of 35th line in the file.txt.
How to get the nth word of a line in Unix?
Assuming
the words in the line are separated by space, we can use the [cut]
command. [cut] is a very powerful and useful command and it's real easy.
All you have to do to get the n-th word from the line is issue the
following command:
cut –f<n> -d' '
'-d'
switch tells [cut] about what is the delimiter (or separator) in the
file, which is space ' ' in this case. If the separator was comma, we
could have written -d',' then. So, suppose I want find the 4th word from
the below string: “A quick brown fox jumped over the lazy cat”, we will
do something like this:
$> echo “A quick brown fox jumped over the lazy cat” | cut –f4 –d' '
And it will print “fox”
How to reverse a string in unix?
Pretty easy. Use the [rev] command.
$> echo "unix" | rev
xinu
How to get the last word from a line in Unix file?
We will make use of two commands that we learnt above to solve this. The commands are [rev] and [cut]. Here we go.
Let's
imagine the line is: “C for Cat”. We need “Cat”. First we reverse the
line. We get “taC rof C”. Then we cut the first word, we get 'taC'. And
then we reverse it again.
$>echo "C for Cat" | rev | cut -f1 -d' ' | rev
Cat
How to get the n-th field from a Unix command output?
We know we can do it by [cut]. Like below command extracts the first field from the output of [wc –c] command
$>wc -c file.txt | cut -d' ' -f1
109
But
I want to introduce one more command to do this here. That is by using
[awk] command. [awk] is a very powerful command for text pattern
scanning and processing. Here we will see how may we use of [awk] to
extract the first field (or first column) from the output of another
command. Like above suppose I want to print the first column of the [wc
–c] output. Here is how it goes like this:
$>wc -c file.txt | awk ' ''{print $1}'
109
The basic syntax of [awk] is like this:
awk 'pattern space''{action space}'
The pattern space can be left blank or omitted, like below:
$>wc -c file.txt | awk '{print $1}'
109
In the action space, we have asked [awk] to take the action of printing the first column ($1). More on [awk] later.
How to replace the n-th line in a file with a new line in Unix?
This
can be done in two steps. The first step is to remove the n-th line.
And the second step is to insert a new line in n-th line position. Here
we go.
Step 1: remove the n-th line
$>sed -i'' '10 d' file.txt # d stands for delete
Step 2: insert a new line at n-th line position
$>sed -i'' '10 i This is the new line' file.txt # i stands for insert
How to show the non-printable characters in a file?
Open
the file in VI editor. Go to VI command mode by pressing [Escape] and
then [:]. Then type [set list]. This will show you all the non-printable
characters, e.g. Ctrl-M characters (^M) etc., in the file.
How to zip a file in Linux?
Use inbuilt [zip] command in Linux
How to unzip a file in Linux?
Use inbuilt [unzip] command in Linux.
$> unzip –j file.zip
How to test if a zip file is corrupted in Linux?
Use “-t” switch with the inbuilt [unzip] command
$> unzip –t file.zip
How to check if a file is zipped in Unix?
In order to know the file type of a particular file use the [file] command like below:
$> file file.txt
file.txt: ASCII text
If you want to know the technical MIME type of the file, use “-i” switch.
$>file -i file.txt
file.txt: text/plain; charset=us-ascii
If the file is zipped, following will be the result
$> file –i file.zip
file.zip: application/x-zip
How to connect to Oracle database from within shell script?
You
will be using the same [sqlplus] command to connect to database that
you use normally even outside the shell script. To understand this,
let's take an example. In this example, we will connect to database,
fire a query and get the output printed from the unix shell. Ok? Here we
go –
$>res=`sqlplus -s username/password@database_name <<EOF
SET HEAD OFF;
select count(*) from dual;
EXIT;
EOF`
$> echo $res
1
If
you connect to database in this method, the advantage is – you will be
able to pass Unix side shell variables value to the database. See below:
$>res=`sqlplus -s username/password@database_name <<EOF
SET HEAD OFF;
select count(*) from customer where last_name='$1';
EXIT;
EOF`
$> echo $res
12
How to execute a database stored procedure from Shell script?
$> SqlReturnMsg=`sqlplus -s username/password@database <<EOF
BEGIN
Proc_Your_Procedure(… your-input-parameters …);
END;
/
EXIT;
EOF`
$> echo $SqlReturnMsg
How to check the command line arguments in a UNIX command in Shell Script?
In
a bash shell, you can access the command line arguments using $0, $1,
$2, … variables, where $0 prints the command name, $1 prints the first
input parameter of the command, $2 the second input parameter of the
command and so on.
How to fail a shell script programmatically?
Just
put an [exit] command in the shell script with return value other than
0. this is because the exit codes of successful Unix programs is zero.
So, suppose if you write
exit -1
inside your program, then your program will thrown an error and exit immediately.
How to list down file/folder lists alphabetically?
Normally
[ls –lt] command lists down file/folder list sorted by modified time.
If you want to list then alphabetically, then you should simply specify:
[ls –l]
How to check if the last command was successful in Unix?
To
check the status of last executed command in UNIX, you can check the
value of an inbuilt bash variable [$?]. See the below example:
$> echo $?
How to check if a file is present in a particular directory in Unix?
Using
command, we can do it in many ways. Based on what we have learnt so
far, we can make use of [ls] and [$?] command to do this. See below:
$> ls –l file.txt; echo $?
If
the file exists, the [ls] command will be successful. Hence [echo $?]
will print 0. If the file does not exist, then [ls] command will fail
and hence [echo $?] will print 1.
How to check all the running processes in Unix?
The
standard command to see this is [ps]. But [ps] only shows you the
snapshot of the processes at that instance. If you need to monitor the
processes for a certain period of time and need to refresh the results
in each interval, consider using the [top] command.
$> ps –ef
If you wish to see the % of memory usage and CPU usage, then consider the below switches
$> ps aux
If
you wish to use this command inside some shell script, or if you want
to customize the output of [ps] command, you may use “-o” switch like
below. By using “-o” switch, you can specify the columns that you want
[ps] to print out.
$>ps -e -o stime,user,pid,args,%mem,%cpu
How to tell if my process is running in Unix?
You
can list down all the running processes using [ps] command. Then you
can “grep” your user name or process name to see if the process is
running. See below:
$>ps -e -o stime,user,pid,args,%mem,%cpu | grep "opera"
14:53 opera 29904 sleep 60 0.0 0.0
14:54 opera 31536 ps -e -o stime,user,pid,arg 0.0 0.0
14:54 opera 31538 grep opera 0.0 0.0
How to get the CPU and Memory details in Linux server?
In Linux based systems, you can easily access the CPU and memory details from the /proc/cpuinfo and /proc/meminfo, like this:
$>cat /proc/meminfo
$>cat /proc/cpuinfo
Just try the above commands in your system to see how it works.
How to display top 10 users Who | head -10 | wc –w?
who | head -10
ls -lrt |tail -10
What is ls -ltd?
ls - ltd
current directory information.
Option l: Long listing
t: Time Stamp
d: Information about current directory
(Used with -l Option)
Saturday, August 11, 2012
DWH,Informatica,Oracle(FAQ)
Data
warehousing concepts (FAQ’s)
1) What is Data warehouse?
Data
warehouse is relational database used for query analysis and reporting. By
definition data warehouse is Subject-oriented, Integrated, Non-volatile, Time
variant.
Subject
oriented : Data warehouse is maintained particular subject.
Integrated :
Data collected from multiple sources integrated into a user readable
unique format.
Non volatile
: Maintain Historical date.
Time
variant : data display the weekly, monthly, yearly.
2) What is Data mart?
A subset
of data warehouse is called Data mart.
3) Difference between Data warehouse and Data mart?
Data
warehouse is maintaining the total organization of data. Multiple data
marts used in data warehouse. where
as data mart is maintained only particular subject.
4) Difference between OLTP and OLAP?
OLTP is
Online Transaction Processing. This is maintained current transactional data.
That means insert, update and delete must be fast.
5) Explain ODS?
Operational
data store is a part of data warehouse. This is maintained only current
transactional data. ODS is subject oriented, integrated, volatile, current
data.
6) Difference between Power Center and Power Mart?
Power
center receive all product functionality including ability to multiple register
servers and metadata across the repository and partition data.
One
repository multiple informatica servers. Power mart received all features except
multiple register servers and partition data.
7) What is a staging area?
Staging area is a temporary storage area used for
transaction, integrated and rather than transaction processing.
When ever your data put in data warehouse you need to clean and process
your data.
8) Explain Additive, Semi-additive, Non-additive facts?
Additive fact: Additive Fact can
be aggregated by simple arithmetical additions.
Semi-Additive fact: semi additive fact can be aggregated simple arithmetical
additions along with some other dimensions.
Non-additive fact: Non-additive fact can’t be added at all.
9) What is a Fact less Fact and example?
Fact table which has no measures.
10) Explain
Surrogate Key?
Surrogate
Key is a series of sequential numbers assigned to be a primary key for the
table.
11) How
many types of approaches in DHW?
Two
approaches: Top-down(Inmol approach), Bottom-up(Ralph Kimball)
12) Explain
Star Schema?
Star
Schema consists of one or more fact table and one or more dimension tables that
are toforeignkeys. Dimension tables are De-normalized, Fact
table-normalized
Advantages: Less database space & Simplify queries.
13)
Explain Snowflake schema?
Snow flake schema is a normalize dimensions to
eliminate the redundancy.The dimension data has been grouped into one large
table. Both dimension and fact tables normalized.
14) What
is confirm dimension?
If both
data marts use same type of dimension that is called confirm dimension.If you
have same type of dimension can be used in multiple fact that is called confirm
dimension.
15) Explain
the DWH architecture?
16) What
is a slowly growing dimension?
Slowly
growing dimensions are dimensional data,there dimensions increasing dimension
data with out update existing dimensions.That means appending new data to
existing dimensions.
17) What
is a slowly changing dimension?
Slowly
changing dimension are dimension data,these dimensions increasing dimensions
data with update existing dimensions.
Type1:
Rows containing changes to existing dimensional are update in the target by
overwriting the existing dimension.In the Type1 Dimension mapping, all rows
contain current dimension data.
Use
the type1 dimension mapping to update a slowly changing dimension table when
you do not need to keep any previous versions of dimensions in the table.
Type2: The
Type2 Dimension data mapping inserts both new and changed dimensions into the
target.Changes are tracked in the target table by versioning the primary key
and creating a version number for each dimension in the table.
Use
the Type2 Dimension/version data mapping to update a slowly changing dimension
when you want to keep a full history of dimension data in the table.version
numbers and versioned primary keys track the order of changes to each
dimension.
Type3: The
type 3 dimension mapping filters source rows based on user-defined comparisions
and inserts only those found to be new dimensions to the target.Rows containing
changes to existing dimensions are updated in the target. When updating an
existing dimension the informatica server saves existing data in different
columns of the same row and replaces the existing data with the updates.
18) When
you use for dynamic cache.
Your
target table is also look up table then you go for dynamic cache .In dynamic
cache multiple matches return an error.use only = operator.
19) what
is lookup override?
Override
the default SQL statement.You can join multiple sources use lookup override.By
default informatica server add the order by clause.
20) we
can pass the null value in lookup transformation?
Lookup
transformation returns the null value or equal to null value.
21) what
is the target load order?
You
specify the target load order based on source qualifiers in a mapping.if u have
the multiple source qualifiers connected to the multiple targets you can
designate the order in which informatica server loads data into the targets.
22) what
is default join that source qualifier provides?
Inner equi
join.
23) what
are the difference between joiner transformation and source qualifier
transformation?
You can
join heterogeneous data sources in joiner transformation, which we cannot
achive in source qualifier transformation.
You need
matching keys to join two relational sources in source qualifier
transformation.where you doesn’t need matching keys to join two sources.
Two
relational sources should come from same data source in source qualifier.You
can join relational sources, which are coming from different sources in source
qualifier.You can join relational sources which are coming from different
sources also.
24) what is update strategy transformation?
Whenever
you create the target table whether you are store the historical data or
current transaction data in to target table.
25) Describe
two levels in which update strategy transformation sets?
26) what
is default source option for update strategy transformation?
Data driven.
27) What
is data driven?
The
information server follows instructions coded into update strategy
transformations with in the session mapping determine how to flag records for
insert,update,delete or reject if u do not choose data driven option setting ,
the informatica server ignores all update strategy transformations in the
mapping.
28) what
are the options in the trarget session of update strategy transformation?
Insert
Delete
Update
Update as update
Update
as insert
Update
else insert
Truncate
table.
29) Difference
between the source filter and filter?
Source
filter is filtering the data only relational sources. Where as filter
transformation filter the data any type of source.
30) what
is a tracing level?
Amount of
information sent to log file.
-- What
are the types of tracing levels?
Normal,Terse,verbose
data,verbose intitialization.
--Expalin
sequence generator transformation?
-- can you
connect multiple ports from one group to multiple transformations?
Yes
31) can
you connect more than one group to the same target or transformation?
NO
32) what
is a reusable transformation?
Reusable transformation can be a single transformation.This transformation can
be used in multiple mappings.when you need to incorporate this transformation
into mapping you add an instance of it to mapping.Later if you change the
definition of the transformation, all instances of it inherit the changes.Since
the instance of reusable transformation is a pointer to that transformation.U can
change the transformation in the transformation developer, its instance
automatically reflect these changes. This feature can save U great deal of
work.
-- what
are the methods for creating reusable transformation?
Two methods
1) Design it in the transformation developer.
2) Promote a standard transformation from the mapping
designer.After you add a transformation to the mapping, you can promote it to
status of reusable transformation.
Once you
promote a standard transformation to reusable status, you can demote it to a
standard transformation at any time.
If u
change the properties of a reusable transformation in mapping , you can revert
it to the original reusable transformation properties by clicking the revert.
33) what
are mapping parameters and mapping variables?
Mapping
parameter represents a constant value that you can define before running a
session.A mapping parameter retains the same value throughout the entire
session.
When you
use the mapping parameter , you declare and use the parameter in a mapping or
mapplet.Then define the value of parameter in a parameter file for the session.
Unlike a
mapping parameter, a mapping variable represents a value that can change
through out the session. The informatica server save the value of mapping
variable to the repository at the end of session run and uses that value next
time you run the session.
34) can
you use the mapping parameters or variables created in one mapping into another
mapping?
NO, we can
use mapping parameters or variables in any transformation of the same mapping
or mapplet in which have crated mapping parameters or variables.
35) Can
you are the mapping parameters or variables created in one mapping into any
other result transformation.
Yes
because the reusable transformation is not contained with any mapplet or
mapping.
36) How
the informatica server sorts the string values in rank transformation?
When the
informatica server runs in the ASCII data movement mode it sorts session data
using binary sort order.If you configures the session to use a binary sort
order, the informatica server calculates the binary value of each string and
returns the specified number of rows with the highest binary values for the
string.
37) What
is the rank index in rank transformation?
The
designer automatically creates a RANKINDEX port for each Rank transformation.
The informatica server uses the Rank Index port to store the ranking position
for each record in a group.For example, if you create a Rank transformation
that ranks the top 5 sales persons for each quarter, the rank index number the
salespeople from 1 to 5.
38) what
is the mapplet?
Mapplet is
a set of transformation that you build in the mapplet designer and you can use
in multiple mappings.
39) Difference
between mapplet and reusable transformation?
Reusable
transformation can be a single transformation.Where as mapplet use multiple
transformations.
40) what
is a parameter a file?
Paramater
file defines the values for parameter and variables.
WORKFLOW
MANAGER
41) what
is a server?
The power
center server moves data from source to targets based on a workflow and mapping
metadata stored in a repository.
42) what
is a work flow?
A workflow
is a set of instructions that describe how and when to run tasks related to
extracting,transformation and loading data.
-- what is session?
A session
is a set of instructions that describes how to move data from source to target
using a mapping.
-- what is
workflow monitor?
Use the
work flow monitor work flows and stop the power center server.
43) explain
a work flow process?
The power center server uses both
process memory and system shared memory to perform these tasks.
Load
manager process: stores
and locks the workflow tasks and start the DTM run the sessions.
Data
Transformation Process DTM: Perform session validations,create threads to initialize the
session,read,write and transform data, and handle pre and post session
operations.
The
default memory allocation is 12,000,000 bytes.
44) What
are types of threads in DTM?
The main
dtm thread is called the master thread.
Mapping
thread.
Transformation
thread.
Reader
thread.
Writer
thread.
Pre-and-post
session thread.
45) Explain
work flow manager tools?
1) Task developer.
2) Work flow designer.
3) Worklet designer.
46) Explain
work flow schedule.
You can
sehedule a work flow to run continuously, repeat at given time or interval or
you manually start a work flow.By default the workflow runs on demand.
47) Explain
stopping or aborting a session task?
If the
power center is executing a session task when you issue the stop the command
the power center stop reading data. If continuous processing and writing data
and committing data to targets.
If the
power center can’t finish processing and committing data you issue the abort
command.
You can
also abort a session by using the Abort() function in the mapping logic.
48) What
is a worklet?
A worklet
is an object that represents a set of taske.It can contain any task available
in the work flow manager. You can run worklets inside a workflow. You can also
nest a worklet in another worklet.The worklet manager does not provide a parameter
file for worklets.
The power
center server writes information about worklet execution in the workflow log.
49) what
is a commit interval and explain the types?
A commit
interval is the interval at which power center server commits data to targets during
a session. The commit interval the number of rows you want to use as a basis
for the commit point.
Target
Based commit: The power center server commits data based on the number of
target rows and the key constraints on the target table. The commit point also
depends on the buffer block size and the commit interval.
Source-based
commit:---------------------------------------------
User-defined
commit:----------------------------------------------
50) Explain
bulk loading?
You can
use bulk loading to improve performance of a session that inserts a large
amount of data to a db2,sysbase,oracle or MS SQL server database.
When bulk
loading the power center server by passes the database log,which speeds
performance.
With out
writing to the database log, however the target database can’t perform
rollback.As a result you may not be perform recovery.
When you
select this option the power center server orders the target load on a
row-by-row basis only.
Edit
tasks->properties->select treat source rows as insert.
Edit
tasks->config object tab->select constraint based
If session
is configured constraint absed loading when target table receive rows from
different sources.The power center server revert the normal loading for those
tables but loads all other targets in the session using constraint based
loading when possible loading the primary key table first then the foreign key
table.
Use the
constraint based loading only when the session option treat rows as set to
insert.
Constraint
based load ordering functionality which allows developers to read the source
once and populate parent and child tables in a single process.
52) Explain
incremental aggregation?
When using
incremental aggregation you apply captured changes in the source to aggregate
calculations 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 power center server to update your target incrementally rather
than forcing it to process the entire source and recalculate the same data each
time you run the session.
You can
capture new source data.use incremental aggregation when you can capture new
source data much time you run the session.Use a stored procedure on filter
transformation only new data.
Incremental
changes do not significantly change the target.Use incremental aggregation when
the changes do not significantly change the target.If processing the
incrementally changed source alters more than half the existing target, the
session may not benefit from using incremental aggregation. In this case drop
the table and recreate the target with complete source data.
53) Processing
of incremental aggregation
The first
time u run an incremental aggregation session the power center server process
the entire source.At the end of the session the power center server stores
aggregate data from the session runs in two files, the index file and the data
file .The power center server creates the files in a local directory.
Transformations.
--- what is transformation?
Transformation
is repository object that generates modifies or passes data.
54) what
are the type of transformations?
2
types:
1) active
2)
passive.
-- explain active and passive transformation?
Active transformation can change the number of rows that pass through it.No of
output rows less than or equal to no of input rows.
Passive transformation does not change the number of rows.Always no of output
rows equal to no of input rows.
55) Difference
filter and router transformation.
Filter
transformation to filter the data only one condition and drop the rows don’t
meet the condition.
Drop rows
does not store any ware like session log file..
Router
transformation to filter the data based on multiple conditions and give yiou
the option to route rows that don’t match to a default group.
56) what
r the types of groups in router transformation?
Router
transformation 2 groups 1. Input group 2. output groups.
Output
groups in 2 types. 1. user defined group 2. default group.
57) difference
between expression and aggregator transformation?
Expression
transformation calculate the single row values before writes the
target.Expression transformation executed by row-by-row basis only.
Aggregator
transformation allows you to perform aggregate calculations like max, min,avg…
Aggregate
transformation perform calculation on groups.
58) How
can u improve the session performance in aggregate transformation?
Use stored input.
59) what
is aggregate cache in aggregate transformation?
The
aggregate stores data in the aggregate cache until it completes aggregate
calculations.When u run a session that uses an aggregate transformation , the
informatica server creates index and data caches in memory is process the
transformation. If the informatica server requires more space it seores
overview values in cache files.
60) explain
joiner transformation?
Joiner transformation joins two
related heterogeneous sources residing in different locations or files.
--What are the types of joins in
joiner in the joiner transformation?
Normal
Master
outer
Detail
outer
Full outer
61) Difference
between connected and unconnected transformations.
Connected
transformation is connected to another transformation with in a mapping.
Unconnected
transformation is not connected to any transformation with in a mapping.
62) In
which conditions we cannot use joiner transformation(limitations of joiner transformation)?
Both
pipelines begin with the same original data source.
Both input
pipelines originate from the same source qualifier transformation.
Both input
pipelines originate from the same normalizer transformation
Both input
pipelines originate from the same joiner transformation.
Either
input pipelines contains an update strategy transformation
Either
input pipelines contains sequence generator transformation.
63) what
are the settings that u use to configure the joiner transformation?
Master and detail source.
Type of join
Condition of the join
64) what
is look up transformation
look up
transformation can be used in a table view based on condition by default lookup
is left outer join
65) why
use the lookup transformation?
To perform
the following tasks.
Get a
related value.For example if your table includes employee ID,but you want to
include such as gross sales per invoice or sales tax but not the calculated
value(such as net sales)
Update
slowly changing dimension tables. You can use a lookup transformation to
determine whether records already exist in the target.
66) what
are the types of lookup?
Connected
and unconnected
67) difference
between connected and unconnected lookup?
|
Connected
lookup
|
Unconnected lookup
|
|
Receives
input values directly from the pipe line.
|
Receives
input values from the result of a clkp expression in a another
transformation.
|
|
U can
use a dynamic or static
Cache
|
U can
use a static cache
|
|
Cache includes
all lokkup columns used in the mapping(that is lookup table columns included
in the lookup condition and lookup table columns linked as output ports to
other transformations)
|
Cache
includes all lookup/output ports in the lookup condition and the lookup/return
port.
|
|
Can
return multiple columns from the same row or insert into the dynamic lookup
cache.
|
Designate
one return port(R).Returns one column from each row.
|
|
If there
is no match for the lookup condition, the informatica server returns the
default value for all output ports.If u configure dynamic caching the
informatica server inserts rows into the cache.
|
If there
is no matching for the lookup condition the informatica server returns
NULL
|
|
Pass
multiple output values to another transformatnion.Link lookup/output ports to
another transformation
|
Pass one
output value to another transformation.The lookup/output/return port passes
the same value to the
---------------------------------------------------------
|
|
Supports
user-defined default values.
|
Does not
support user-defined default values.
|
68) explain
index cache and data cache?
The
informatica server stores conditions values in the index cache and output
values in the data cache.
69) What
are the types of lookup cache?
Persistent
cache: U can save the look up cache files and reuse them the next time the
informatica server processes a lookup transformation to use the cache.
Static
cache: U can configure a static or read-only lookup table.By default
informatica server creates a static cache.It caches the lookup table and lookup
values in the cache for each row that comes into the transformation.When the
lookup condition is true the inforamtica server does not update the cache while
it processes the lookup transformation.
Dynamic
cache: If you want to cache the target table and insert new rows into cache and
the target you can create a look up transformation to use dynamic cache.The
informatica server dynamically inserts data into the target
table.
Shared
cache: You can share the lookup cache between multiple transformations.You can
share unnamed cache between transformation in the same mapping.
70) Difference
between static cache and dynamic cache?
|
Static cache
|
Dynamic cache
|
|
You
cannot insert or update the cache
|
You can
insert rows into the cache as you pass rows to the target
|
|
The
informatica server returns a value from the lookup table or cache when the
condition is true,.When the condition is true the informatica server returns
the default value for connected transformation
|
The
informatica server inserts rows into the cache when the condition is
false.This indicates that the row in the cache or target table.You can pass
these rows to the target table.
|
ORACLE:
71) Difference
between primary key and unique key?
Primary
key is Not null unique
Unique
accept the null values.
72) Difference
between inserting and sub string?
73) What
is referential integrity?
74) Difference
between view and materialized view?
75) What
is Redolog file?
The
set of redo log files for a database is collectively know as the databases redo
log.
76) What
is RollBack statement?
A database
contains one or more rollback segments to temporarily store undo
information.Roll back segment are used to generate read consistant data base
information during database recovery to rooback uncommitted transactions for
users.
-- what is table space?
A data
base is divided into logical storage unit called table space.A table space is
used to grouped related logical structures together.
-- How to delete the duplicate
records.
-- What are the difference types of
joins in Oracle?
Self-join,equi-join,outer join.
77) What
is outer join?
One of
which rows that don’t match those in the commen column of another table.
78) write
query Max 5 salaries?
Select *
from emp e where 5>(select count(*) from emp where sal>e.sal)
79) what
is synonym?
82) What
is bit map index and example?
83) What
is stored procedure and advantages?
84) Explain
cursor and how many types of triggers in oracle?
Trigger is
stored procedure.Trigger is automatically executed.
85) Difference
between function and stored procedure?
Function returns a value.Procedure
does not return a value(but returns a value tru IN OUT parameters!!!!!!)
86) Difference
between replace and translate?
87) Write
the query nth max sal
Select
distinct (a.sal) from emp a where &n=select count(distinct(b.sal) from emp
b where a.sal<=b.sal
88) Write
the query odd and even numbers?
Select *
from emp where (rowed,1) in (select rowed,mod(rownum,2) from emp)
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