Welcome to the finest collection of Informatica Interview Questions with standard answers that you can count on. Read and understand all the questions and their answers below and in the following pages to get a good grasp in Informatica.
What are the differences between Connected and Unconnected Lookup?Connected LookupUnconnected LookupConnected lookup participates in dataflow and receives input directly from the pipelineUnconnected lookup receives input values from the result of a LKP: expression in another transformationConnected lookup can use both dynamic and static cacheUnconnected Lookup cache can NOT be dynamicConnected lookup can return more than one column value ( output port )Unconnected Lookup can return only one column value i.e. output portConnected lookup caches all lookup columnsUnconnected lookup caches only the lookup output ports in the lookup conditions and the return portSupports user-defined default values (i.e. value to return when lookup conditions are not satisfied)Does not support user defined default valuesWhat is the difference between Router and Filter?RouterFilterRouter transformation divides the incoming records into multiple groups based on some condition. Such groups can be mutually inclusive (Different groups may contain same record)Filter transformation restricts or blocks the incoming record set based on one given condition.Router transformation itself does not block any record. If a certain record does not match any of the routing conditions, the record is routed to default groupFilter transformation does not have a default group. If one record does not match filter condition, the record is blockedRouter acts like CASE.. WHEN statement in SQL (Or Switch().. Case statement in C)Filter acts like WHERE condition is SQL.What can we do to improve the performance of Informatica Aggregator Transformation?Aggregator performance improves dramatically if records are sorted before passing to the aggregator and "sorted input" option under aggregator properties is checked. The record set should be sorted on those columns that are used in Group By operation.
It is often a good idea to sort the record set in database level (why?) e.g. inside a source qualifier transformation, unless there is a chance that already sorted records from source qualifier can again become unsorted before reaching aggregator
What are the different lookup cache?Lookups can be cached or uncached (No cache). Cached lookup can be either static or dynamic. A static cache is one which does not modify the cache once it is built and it remains same during the session run. On the other hand, A dynamic cache is refreshed during the session run by inserting or updating the records in cache based on the incoming source data.
A lookup cache can also be divided as persistent or non-persistent based on whether Informatica retains the cache even after session run is complete or not respectively
How can we update a record in target table without using Update strategy?A target table can be updated without using 'Update Strategy'. For this, we need to define the key in the target table in Informatica level and then we need to connect the key and the field we want to update in the mapping Target. In the session level, we should set the target property as "Update as Update" and check the "Update" check-box.
Let's assume we have a target table "Customer" with fields as "Customer ID", "Customer Name" and "Customer Address". Suppose we want to update "Customer Address" without an Update Strategy. Then we have to define "Customer ID" as primary key in Informatica level and we will have to connect Customer ID and Customer Address fields in the mapping. If the session properties are set correctly as described above, then the mapping will only update the customer address field for all matching customer IDs.