informatica interview questions.doc

7/25/2019 informatica interview questions.doc

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What are the differences between Connected and Unconnected Lookup?

Connected Lookup Unconnected Lookup

Connected lookup participates indataflow and receives input directly

from the pipeline

Unconnected lookup receives inputvalues from the result of a LKP:

expression in another transformation

Connected lookup can use both dynamic

and static cache

Unconnected Lookup cache can NO be

dynamic

Connected lookup can return more than

one column value ! output port "

Unconnected Lookup can return only

one column value i#e# output port

Connected lookup caches all lookupcolumns

Unconnected lookup caches only thelookup output ports in the lookup

conditions and the return port

$upports user%defined default values !i#e#

value to return when lookup conditionsare not satisfied"

&oes not support user defined defaultvalues

What is the difference between Router and Filter?

Router Filter

'outer transformation divides theincomin( records into multiple (roups

based on some condition# $uch (roups

can be mutually inclusive !&ifferent(roups may contain same record"

)ilter transformation restricts or blocks

the incomin( record set based on one

(iven condition#

'outer transformation itself does notblock any record# *f a certain record does

not match any of the routin( conditions+the record is routed to default (roup

)ilter transformation does not have adefault (roup# *f one record does not

match filter condition+ the record isblocked

'outer acts like C,$-## ./-N

statement in $0L !Or $witch!"## Case

statement in C"

)ilter acts like ./-'- condition is

$0L#


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What can we do to improve the performance of Informatica Aggregator

ransformation?

,((re(ator performance improves dramatically if records are sorted before passin( to thea((re(ator and 1sorted input1 option under a((re(ator properties is checked# he record

set should bbe sorted on those columns that are used in 2roup 3y operation#

*t is often a (ood idea to sort the record set in database level !why4" e#(# inside a source

5ualifier transformation+ unless there is a chance that already sorted records from source5ualifier can a(ain become unsorted before reachin( a((re(ator

What are the different lookup cache?

Lookups can be cached or uncached !No cache"# Cached lookup can be either static ordynamic# , static cacheis one which does not modify the cache once it is built and it

remains same durin( the session run# On the other hand+ , d!namic cacheis refreshed

durin( the session run by insertin( or updatin( the records in cache based on theincomin( source data#

, lookup cache can also be divided as persistent or non"persistentbased on whether

*nformatica retains the cache even after session run is complete or not respectively

#ow can we update a record in target table without using Update

strateg!?

, tar(et table can be updated without usin( 6Update $trate(y6# )or this+ we need to definethe key in the tar(et table in *nformatica level and then we need to connect the key and

the field we want to update in the mappin( ar(et# *n the session level+ we should set thetar(et property as 1Update as Update1 and check the 1Update1 check%box#

Let6s assume we have a tar(et table 1Customer1 with fields as 1Customer *&1+ 1Customer

Name1 and 1Customer ,ddress1# $uppose we want to update 1Customer ,ddress1

without an Update $trate(y# hen we have to define 1Customer *&1 as primary key in

*nformatica level and we will have to connect Customer *& and Customer ,ddress fieldsin the mappin(# *f the session properties are set correctly as described above+ then the

mappin( will only update the customer address field for all matchin( customer *&s#

$eleting duplicate row using Informatica

%&' $uppose we have $uplicate records in $ource $ystem and we want to load only the

uni5ue records in the ar(et $ystem eliminatin( the duplicate rows# .hat will be the

approach4

Ans'

Let us assume that the source system is a Relational $atabase # he source table is

havin( duplicate rows# Now to eliminate duplicate records+ we can check the $istinctoption of the (ource %ualifierof the source table and load the tar(et accordin(ly#
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$ource 0ualifier ransformation &*$*NC clause

, collection of scenario based *nformatica *nterview 0uestions#

$eleting duplicate row for FLA FIL) sources

Now suppose the source system is a Flat File# /ere in the $ource 0ualifier you will notbe able to select the distinct clause as it is disabled due to flat file source table# /ence thenext approach may be we use a (orter ransformationand check the $istinctoption#

.hen we select the distinct option all the columns will the selected as keys+ in ascendin(

order by default#


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$orter ransformation &*$*NC clause

$eleting $uplicate Record Using Informatica Aggregator

Other ways to handle duplicate records in source batch run is to use an Aggregatorransformationand usin( the *roup +!checkbox on the ports havin( duplicate

occurrin( data# /ere you can have the flexibility to select the last or the firstof theduplicate column value records# ,part from that usin( $!namic Lookup Cacheof the

tar(et table and associatin( the input ports with the lookup port and checkin( the *nsert

-lse Update option will help to eliminate the duplicate records in source and henceloadin( uni5ue records in the tar(et#

)or more details on &ynamic Lookup Cache

Loading ,ultiple arget ables +ased on Conditions

%-' $uppose we have some serial numbers in a flat file source# .e want to load the serial

numbers in two tar(et files one containin( the -7-N serial numbers and the other filehavin( the O&& ones#

Ans'

,fter the $ource 0ualifier place a Router ransformation # Create two *roupsnamely

).)/ and 0$$+ with filter conditions as ,0$1()RIAL2/03-456 and

,0$1()RIAL2/03-45& respectively# hen output the two (roups into two flat file

tar(ets#
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'outer ransformation 2roups ab

/ormali7er Related %uestions

%8' $uppose in our $ource able we have data as (iven below:

$tudent Name 8aths Life $cience Physical $cience

$am 9 ; 9

om


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$am Life $cience ;

$am Physical $cience

=ohn Life $cience 9

=ohn Physical $cience

om 8aths


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se5uence numbers for each source row from the port /e;t.al of a (e


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%>' /ow can we implement ,((re(ation operation without usin( an ,((re(ator

ransformation in *nformatica#

Ans'

.e will use the very basic concept of the );pression ransformation that at a time we

can access the previous row data as well as the currently processed data in an expressiontransformation# .hat we need is simple $orter+ -xpression and )ilter transformation to

achieve a((re(ation at *nformatica level#

)or detailed understandin( visit ,((re(ation without ,((re(ator

%' $uppose in our $ource able we have data as (iven below:

$tudent Name $ub?ect Name 8arks

$am 8aths 9

om 8aths


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L*)-B$C: 8,F!8,'K$+ $U3=-CD6Life $cience6"

P/GB$C: 8,F!8,'K$+ $U3=-CD6Physical $cience6"

,((re(ator ransformation

Revisiting (ource %ualifier ransformation

%B' .hat is a $ource 0ualifier4 .hat are the tasks we can perform usin( a $0 and whyit is an ,C*7- transformation4

Ans'

, (ource %ualifieris an ,ctive and Connected *nformatica transformation that reads the

rows from a relational database or flat file source#

.e can confi(ure the (%tooinH3oth I//)Ras well as 0U)R D0I/I data

ori(inatin( from the same source database#.e can use a source filterto reduce the number of rows the *nte(ration $ervice 5ueries#

.e can specify a number for sorted portsand the *nte(ration $ervice adds an O'&-'3G clause to the default $0L 5uery#

.e can choose (elect $istinct option for relational databases and the *nte(ration $ervice

adds a $-L-C &*$*NC clause to the default $0L 5uery#,lso we can write CustomEUsed $efined (%L 5uery which will override the default

5uery in the $0 by chan(in( the default settin(s of the transformation properties#


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,slo we have the option to write @re as well as @ost (%L statements to be executed

before and after the $0 5uery in the source database#

$ince the transformation provides us with the property (elect $istinct + when the

*nte(ration $ervice adds a $-L-C &*$*NC clause to the default $0L 5uery+ which in

turn affects the number of rows returned by the &atabase to the *nte(ration $ervice andhence it is an ,ctive transformation#

%&6' .hat happens to a mappin( if we alter the datatypes between $ource and its

correspondin( $ource 0ualifier4

Ans'

he $ource 0ualifier transformation displays the transformation datatypes# he

transformation datatypes determine how the source database binds data when the*nte(ration $ervice reads it#

Now if we alter the datatypes in the $ource 0ualifier transformation or the datat!pes in

the source definition and (ource %ualifier transformation do not match3the&esi(ner marks the mapping as invalid when we save it#

%&&' $uppose we have used the $elect &istinct and the Number Of $orted Ports property

in the $0 and then we add Custom $0L 0uery# -xplain what will happen#

Ans'

.henever we add Custom $0L or $0L override 5uery it overrides the User%&efined

=oin+ $ource )ilter+ Number of $orted Ports+ and $elect &istinct settin(s in the $ource

0ualifier transformation# /ence only the user defined $0L 0uery will be fired in thedatabase and all the other options will be ignored #

%&-' &escribe the situations where we will use the $ource )ilter+ $elect &istinct and

Number Of $orted Ports properties of $ource 0ualifier transformation#

Ans'

(ource Filter option is used basically to reduce the number of rows the *nte(ration

$ervice 5ueries so as to improve performance#

(elect $istinct option is used when we want the *nte(ration $ervice to select uni5ue

values from a source+ filterin( out unnecessary data earlier in the data flow+ which mi(ht

improve performance#

/umber 0f (orted @orts option is used when we want the source data to be in a sorted

fashion so as to use the same in some followin( transformations like ,((re(ator or

=oiner+ those when confi(ured for sorted input will improve the performance#

%&8' .hat will happen if the $-L-C list COLU8N$ in the Custom override $0L0uery and the OUPU PO'$ order in $0 transformation do not match4

Ans'


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8ismatch or Chan(in( the order of the list of selected columns to that of the connected

transformation output ports may result is session failure'

%&9' .hat happens if in the $ource )ilter property of $0 transformation we includekeyword ./-'- say+ ./-'- CU$O8-'$#CU$O8-'B*& J 9#

Ans'

.e use source filter to reduce the number of source records# *f we include the strin(

W#)R) in the source filter+ the *nte(ration $ervice fails the session #

%&:' &escribe the scenarios where we (o for =oiner transformation instead of $ource

0ualifier transformation#

Ans'

.hile ?oinin( $ource &ata of heterogeneous sources as well as to ?oin flat files we will

use the =oiner transformation#

Use the =oiner transformation when we need to ?oin the followin( types of sources:=oin data from different 'elational &atabases#

=oin data from different )lat )iles#=oin relational sources and flat files#

%&=' .hat is the maximum number we can use in Number Of $orted Ports for $ybase

source system#

Ans'

$ybase supports a maximum of &= columns in an O'&-' 3G clause# $o if the source is

$ybase+ do not sort more than 9 columns#

%&>' $uppose we have two $ource 0ualifier transformations $09 and $0E connected toar(et tables 29 and 2E respectively# /ow do you ensure 2E is loaded after

294

Ans'

*f we have multiple $ource 0ualifier transformations connected to multiple tar(ets+ we

can desi(nate the order in which the *nte(ration $ervice loads data into the tar(ets#*n the 8appin( &esi(ner+ .e need to confi(ure the arget Load @lanbased on the

$ource 0ualifier transformations in a mappin( to specify the re5uired loadin( order#

*ma(e: ar(et Load Plan
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ar(et Load Plan Orderin(

%&' $uppose we have a $ource 0ualifier transformation that populates two tar(et tables#/ow do you ensure 2E is loaded after 294

Ans'

*n the .orkflow 8ana(er+ we can Confi(ure Constraint based load ordering for a

session# he *nte(ration $ervice orders the tar(et load on a row%by%row basis# )or everyrow (enerated by an active source+ the *nte(ration $ervice loads the correspondin(

transformed row first to the primary key table+ then to the forei(n key table#/ence if we have one $ource 0ualifier transformation that provides data for multiple

tar(et tables havin( primary and forei(n key relationships+ we will (o for Constraint

based load orderin(#

*ma(e: Constraint based loadin(

Revisiting Filter ransformation

%&B' .hat is a )ilter ransformation and why it is an ,ctive one4

Ans'

, Filter transformation is an Active and Connected transformation that can filter rows in

a mappin(#

Only the rows that meet the Filter Conditionpass throu(h the )ilter transformation to

the next transformation in the pipeline# 'U- and ),L$- are the implicit return valuesfrom any filter condition we set# *f the filter condition evaluates to NULL+ the row is
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assumed to be ),L$-#

he numeric e5uivalent of ),L$- is @ero !" and any non%@ero value is the e5uivalent of

'U-#

,s an ACI.) transformation+ the )ilter transformation may chan(e the number of rows

passed throu(h it# , filter condition returns 'U- or ),L$- for each row that passesthrou(h the transformation+ dependin( on whether a row meets the specified condition#

Only rows that return 'U- pass throu(h this transformation# &iscarded rows do not

appear in the session lo( or re?ect files#

%-6' .hat is the difference between $ource 0ualifier transformations $ource )ilter to)ilter transformation4

Ans'

$0 $ource )ilter )ilter ransformation

$ource 0ualifier

transformation filters

rows when read from asource#

)ilter transformation filters rows

from within a mappin(

$ource 0ualifiertransformation can only

filter rows from

'elational $ources#

)ilter transformation filters rowscomin( from any type of source

system in the mappin( level#

$ource 0ualifier limits

the row set extracted

from a source#

)ilter transformation limits the

row set sent to a tar(et#

$ource 0ualifier reducesthe number of rows used

throu(hout the mappin(

and hence it providesbetter performance#

o maximi@e session

performance+ include the )iltertransformation as close to the

sources in the mappin( as

possible to filter out unwanteddata early in the flow of data

from sources to tar(ets#

he filter condition in

the $ource 0ualifier

transformation only usesstandard $0L as it runs

)ilter ransformation can define

a condition usin( any statement

or transformation function thatreturns either a 'U- or ),L$-


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in the database# value#

Revisiting Doiner ransformation

%-&' .hat is a =oiner ransformation and why it is an ,ctive one4

Ans'

, Doiner is an Active and Connected transformation used to ?oin source data from the

same source system or from two related hetero(eneous sources residin( in differentlocations or file systems#

he =oiner transformation ?oins sources with at least one matchin( column# he =oiner

transformation uses a condition that matches one or more pairs of columns between thetwo sources#

he two input pipelines include a master pipeline and a detail pipeline or a master and a

detail branch# he master pipeline ends at the =oiner transformation+ while the detailpipeline continues to the tar(et#

*n the =oiner transformation+ we must confi(ure the transformation properties namely

=oin Condition+ =oin ype and $orted *nput option to improve *nte(ration $erviceperformance#

he ?oin condition contains ports from both input sources that must match for the

*nte(ration $ervice to ?oin two rows# &ependin( on the type of ?oin selected+ the*nte(ration $ervice either adds the row to the result set or discards the row #

he =oiner transformation produces result sets based on the ?oin type+ condition+ and

input data sources# /ence it is an ,ctive transformation#

%--' $tate the limitations where we cannot use =oiner in the mappin( pipeline#

Ans'

he =oiner transformation accepts input from most transformations# /owever+ followin(are the limitations:

=oiner transformation cannot be used when either of the input pipeline contains an

Update (trateg!transformation#=oiner transformation cannot be used if we connect a (e


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o improve performance for an Unsorted Doiner transformation+ use the source with

fewer rows as the master source# he fewer uni5ue rows in the master+ the feweriterations of the ?oin comparison occur+ which speeds the ?oin process#

.hen the *nte(ration $ervice processes an unsorted =oiner transformation+ it reads all

master rows before it reads the detail rows# he *nte(ration $ervice blocks the detailsource while it caches rows from the master source # Once the *nte(ration $ervice reads

and caches all master rows+ it unblocks the detail source and reads the detail rows#

o improve performance for a (orted Doiner transformation+ use the source with fewer

duplicate ke! values as the master source#

.hen the *nte(ration $ervice processes a sorted =oiner transformation+ it blocks data

based on the mappin( confi(uration and it stores fewer rows in the cache+ increasin(performance# 3lockin( lo(ic is possible if master and detail input to the =oiner

transformation ori(inate from different sources # Otherwise+ it does not use blockin(

lo(ic# *nstead+ it storesmore rows in the cache#

%-9' .hat are the different types of =oins available in =oiner ransformation4

Ans'

*n $0L+ a ?oin is a relational operator that combines data from multiple tables into asin(le result set# he =oiner transformation is similar to an $0L ?oin except that data can

ori(inate from different types of sources#

he =oiner transformation supports the followin( t!pes of oins:

/ormal

,aster 0uter

$etail 0uter

Full 0uter


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=oin ype property of =oiner ransformation

/ote , normal or master outer?oin performs faster than a full outer or detail outer?oin#

%-:' &efine the various =oin ypes of =oiner ransformation#

Ans'

*n a normal oin+ the *nte(ration $ervice discards all rows of data from the master and

detail source that do not match+ based on the ?oin condition#

, master outer oin keeps all rows of data from the detail source and the matchin( rowsfrom the master source# *t discards the unmatched rows from the master source#

, detail outer?oin keeps all rows of data from the master source and the matchin( rows

from the detail source# *t discards the unmatched rows from the detail source#

, full outer?oin keeps all rows of data from both the master and detail sources#

%-=' &escribe the impact of number of ?oin conditions and ?oin order in a =oiner

ransformation#

Ans'

.e can define one or more conditionsbased on e


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and detail sources#

3oth ports in a condition must have the same datat!pe # *f we need to use two ports in

the ?oin condition with non%matchin( datatypes we must convert the datatypes so thatthey match# he &esi(ner validates datatypes in a ?oin condition#

Additional ports in the ?oin condition increases the time necessary to ?oin two sources#

he order of the ports in the ?oin condition can impact the performance of the =oiner

transformation# *f we use multiple ports in the ?oin condition+ the *nte(ration $ervice

compares the ports in the order we specified#

/0) Only e5uality operator is available in ?oiner ?oin condition#

%->' /ow does =oiner transformation treat NULL value matchin(#

Ans'

he =oiner transformation does not match null values #

)or example+ if both -8PB*&9 and -8PB*&E contain a row with a null value+ the*nte(ration $ervice does not consider them a match and does not ?oin the two rows#

o ?oin rows with null values+ replace null input with default values in the Ports tab of

the ?oiner+ and then ?oin on the default values#

/ote *f a result set includes fields that do not contain data in either of the sources+ the

=oiner transformation populates the empty fields with null values# *f we know that a field

will return a NULL and we do not want to insert NULLs in the tar(et+ set a default valueon the Ports tab for the correspondin( port#

%-' $uppose we confi(ure $orter transformations in the master and detail pipelines with

the followin( sorted ports in order: *-8BNO+ *-8BN,8-+ P'*C-#.hen we confi(ure the ?oin condition+ what are the (uidelines we need to follow tomaintain the sort order4

Ans'

*f we have sorted both the master and detail pipelines in order of the ports say

*-8BNO+ *-8BN,8- and P'*C- we must ensure that:

Use *-8BNO in the )irst =oin Condition#*f we add a $econd =oin Condition+ we must use *-8BN,8-#

*f we want to use P'*C- as a =oin Condition apart from *-8BNO+ we must also use

*-8BN,8- in the $econd =oin Condition#

*f we skip *-8BN,8- and ?oin on *-8BNO and P'*C-+ we will lose the input sort

order and the *nte(ration $ervice fails the session #

%-B' .hat are the transformations that cannot be placed between the sort ori(in and the

=oiner transformation so that we do not lose the input sort order#

Ans'

he best option is to place the =oiner transformation directly after the sort ori(in to


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maintain sorted data#

/owever do not place any of the followin( transformations between the sort ori(in and

the =oiner transformation:

Custom

Unsorted ,((re(atorNormali@er

'ank

Union transformationF8L Parser transformation

F8L 2enerator transformation

8applet Hif it contains any one of the above mentioned transformationsI

%86' $uppose we have the -8P table as our source# *n the tar(et we want to view thoseemployees whose salary is (reater than or e5ual to the avera(e salary for their

departments#

&escribe your mappin( approach#Ans'Our 8appin( will look like this:

*ma(e: 8appin( usin( =oiner

o start with the mappin( we need the followin( transformations:

,fter the $ource 5ualifier of the -8P table place a (orter ransformation # $ort based

on $)@/0port#
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$orter Ports ab

Next we place a (orted Aggregator ransformation # /ere we will find out theA.)RA*) (ALAR for each !2'OUP 3G" $)@/0 #

.hen we perform this a((re(ation+ we lose the data for individual employees# o

maintain employee data+ we must pass a branch of the pipeline to the ,((re(atorransformation and pass a branch with the same sorted source data to the =oiner

transformation to maintain the ori(inal data# .hen we ?oin both branches of the pipeline+

we ?oin the a((re(ated data with the ori(inal data#


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,((re(ator Ports ab


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,((re(ator Properties ab

$o next we need (orted Doiner ransformation to ?oin the sorted a((re(ated data withthe ori(inal data+ based on $)@/0 #

/ere we will be takin( the a((re(ated pipeline as the 8aster and ori(inal dataflow as

&etail Pipeline#


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=oiner Condition ab


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=oiner Properties ab

,fter that we need a Filter ransformation to filter out the employees havin( salary lessthan avera(e salary for their department#

)ilter Condition: (ALG5A.*2(AL


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)ilter Properties ab

Lastly we have the ar(et table instance#

Revisiting (e


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%8-' &efine the Properties available in $e5uence 2enerator transformation in brief#

Ans'

$e5uence

2enerator

Properties

&escription

$tart 7alue

$tart value of the (enerated se5uence that we

want the *nte(ration $ervice to use if we usethe Cycle option# *f we select Cycle+ the

*nte(ration $ervice cycles back to this value

when it reaches the end value#&efault is #

*ncrement3y

&ifference between two consecutive values

from the N-F7,L port#&efault is 9#

-nd 7alue

8aximum value (enerated by $e52en# ,fter

reachin( this value the session will fail if the

se5uence (enerator is not confi(ured to

cycle#&efault is E9;


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each time a session runs#his option is disabled for reusable $e5uence

2enerator transformations#

%88' $uppose we have a source table populatin( two tar(et tables# .e connect the

N-F7,L port of the $e5uence 2enerator to the surro(ate keys of both the tar(et tables#.ill the $urro(ate keys in both the tar(et tables be same4 *f not how can we flow the

same se5uence values in both of them#

Ans'

.hen we connect the /)H.AL output port of the (e" and 2E !+;+


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%89' $uppose we have 9 records comin( from the source# Now for a tar(et column

population we used a $e5uence (enerator#$uppose the Current 7alue is and -nd 7alue of $e5uence (enerator is set to

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