Flat File Lookup: When we use a flat file for a lookup source, we can use any flat file definition in the repository, or we can import it. As DEPT is the Source definition, click Source and then Select DEPT.
When we import a flat file lookup source, the Designer invokes the Flat File Wizard.
Define these options in the Transformations view on Mapping tab of the session properties.
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Make it Input port only and Give Datatype same as DEPTNO. The IS does not update the cache while it processes the Lookup transformation. Dynamic Cache To cache a target table or flat file source and insert new rows or update existing rows in the cache, use a Lookup transformation with a dynamic cache. The IS saves and reuses cache files from session to session, eliminating the time Required to read the lookup table. Recache from Source If the persistent cache is not synchronized with the lookup table, we can Configure the Lookup transformation to rebuild the lookup cache.
As DEPTNO is common in source and Lookup, create a port IN_DEPTNO ports tab. It caches the lookup file or table and Looks up values in the cache for each row that comes into the transformation. Persistent Cache If the lookup table does not change between sessions, we can configure the Lookup transformation to use a persistent lookup cache.
When session completes, IS releases cache memory and deletes the cache files. Static Cache By default, the IS creates a static cache.
We compare transformation input values with values in the lookup source or cache, represented by lookup ports.
In_DNAME = 'DELHI' Tip: If we include more than one lookup condition, place the conditions with an equal sign first to optimize lookup performance.
Open the Expression editor and call Lookup as given below: We double click Unconn in bottom of Functions tab and as we need only DEPTNO, we pass only DEPTNO as input. Validate the call in Expression editor and Click OK. The Integration Service (IS) builds a cache in memory when it processes the first row of data in a cached Lookup transformation.