when will we use unconnected & connected lookup? How it
will effect on the performance of mapping?

Answer Posted / sweta kedia

A. Connected Lookup
Receives input values directly from the pipeline.
We can use a dynamic or static cache
Supports user-defined default values

Unconnected Lookup
Receives input values from the result of a :LKP expression
in another transformation.
We can use a static cache
Does not support user-defined default values

When you compared both basically connected lookup will
return more values and unconnected returns one value. conn
lookup is in the same pipeline of source and it will accept
dynamic caching. Unconn lookup don't have that faclity but
in some special cases we can use Unconnected. if output of
one lookup is going as input of another lookup this
unconnected lookups are favourable
Moreover if the mapping requires multiple lookup using same
lookup conditions then its better to use unconnected lookup
& call the lookup wherever required.This also prevents the
mapping from being complex.

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