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
What is meant by lookup transformation?
Please tell me which institute is the best to study Informatica and asp.net in chennai Also please send me the latest interview questions in asp.net,c# and sql server to my id ramtryin@gmail.com
How to create a non-reusable instance of reusable transformations?
Enlist the differences between database and data warehouse.
What do mean by local and global repository?
how will u take the data from clint server and next what u do in datamodeling what u will u do in staging area what u will u do next what u are doing please give the step by step by process
Differences between connected and unconnected lookup?
Tell me can we override a native sql query within informatica? Where do we do it? How do we do it?
How do you use reject loader.
Explain the types of transformations?
How to go to the older version for a mapping?
What is the status code in stored procedure transformation?
Describe an informatica powercenter?
what is the Default Source Option For Update Strategy Transformation?
What are the components of the workflow manager?
