The Use of UNConnected Lookup

The use of unconnected lookup transformation.

1) The big question is why should we use unconnected lkp transformation,
if we can achieve same with connected one?

2) Which gives better performance, connected or unconnected and why?

Answers 1 :
Depending upon the scenario that we have we use the connected and unconnected LKP..

Scenario:
In our scenario we need to lookup multiple times,creating lkp multiple times and putting it in flow is not a good idea..bcoz it
will create more cache and thus deteroiting the performance
Instead of that we can create one unconnected lookup use it multiple times where ever u want which will be much more faster.

Answers 2:
You can use conn lookup but if u need 1 row so u can go for unconnected lKP becoz u can
use it multiple time in same mapping from multiple expression transformation.

Benefit of the above approach :
The benefit of an uncncted lKP is that you can do conditional lookups (using IIF,DECODE, etc.).
In other words, you can control the lookup in unconnected lookup.

Uncnted LKP gives better performance because it's not connectd to mapping pipeline.
so data transform is faster compared to connected one

Unconnected lookup can be used when we need only one returning port from the lookup table or if the same lookup condition is used
many times in the mapping. And moreover unconnected lookup gives
better performance as it just acts as a function call. but if
more than one ports has to be returned from look up table then we must use a
connected lookup.