Answer Posted / sandeep
Differences Between Connected and Unconnected Lookup:
connected
o Receives input values directly from the pipeline.
o uses Dynamic or static cache
o Returns multiple values
o supports user defined default values.
Unconnected
o Recieves input values from the result of LKP
expression in another transformation
o Use static cache only.
o Returns only one value.
o Doesn’t supports user-defined default values.
NOTES
o Common use of unconnected LKP is to update slowly
changing dimension tables.
o Lookup components are
(a) Lookup table. B) Ports c) Properties d) condition.
Lookup tables: This can be a single table, or you can
join multiple tables in the same Database using a Lookup
query override.You can improve Lookup initialization time
by adding an index to the Lookup table.
Lookup ports: There are 3 ports in connected LKP
transformation (I/P,O/P,LKP) and 4 ports unconnected LKP
(I/P,O/P,LKP and return ports).
o if you’ve certain that a mapping doesn’t use a
Lookup ,port ,you delete it from the transformation. This
reduces the amount of memory.
Lookup Properties: you can configure properties such as SQL
override .for the Lookup,the Lookup table name ,and tracing
level for the transformation.
Lookup condition: you can enter the conditions ,you want
the server to use to determine whether input data qualifies
values in the Lookup or cache .
when you configure a LKP condition for the transformation,
you compare transformation input values with values in the
Lookup table or cache ,which represented by LKP ports .when
you run session ,the server queries the LKP table or cache
for all incoming values based on the condition.
NOTE
- If you configure a LKP to use static cache ,you
can following operators =,>,<,>=,<=,!=.
but if you use an dynamic cache only =can be used .
- when you don’t configure the LKP for caching ,the
server queries the LKP table for each input row .the result
will be same, regardless of using cache
However using a Lookup cache can increase session
performance, by Lookup table, when the source table is
large.
Performance tips:
- Add an index to the columns used in a Lookup
condition.
- Place conditions with an equality opertor (=) first.
- Cache small Lookup tables .
- Don’t use an ORDER BY clause in SQL override.
- Call unconnected Lookups with :LKP reference
qualifier.
| Is This Answer Correct ? | 17 Yes | 2 No |
Post New Answer View All Answers
How you know when to use a static cache and dynamic cache in lookup transformation?
Could you explain what is enterprise data warehouse?
What is meant by a domain?
What is informatica metadata and where is it stored?
What are the conditions needed to improve the performance of informatica aggregator transformation?
How can you generate reports in informatica?
In how many ways we can create ports?
What is confirmed fact in dataware housing?
Hello , I am unable to work with SQL transformation at least. Where do i need to give connection for sql transformaton ? At session level there is no property . I have created a SQL Transformation and chosen query mode. But do i need to pass connection information to it ? I don't know where do i need to write a query ? I have written a query in file and that file path i gave in the properties of SQL Transformation. But it is not working. Could any one of you please let know how can i work with SQL Transformation? Advance Thanks.
What are the transformations that cannot be placed between the sort origin and the joiner transformation so that we do not lose the input sort order?
What is mapplet in informatica?
What is the surrogate key?
How to generate sequence numbers without using the sequence generator transformation?
What are the limitations of joiner transformation?
what is mean by complex business rule ?
