Delete Flag

Lets say a record is deleted in source which is already available in target,Requirement is to have a column DELETE_FLAG in target and stores 'Y' for the records
deleted in source else 'N'

Source table: SRC_EMP

Target Table: TGT_EMP

Add D_FLAG column to TGT_EMP

Import Source table to Informatica as Source.
Import Target table to Informatica as both Source and Target.

Use Joiner Transformations as below

Use Expression Transformation as below

Use Update Strategy as below

 Final mapping looks like below

Workflow Designer:
session >
Properties >Target Source Row as - Update
Mapping > SQ_SRC_EMP should be Source
Mapping > SQ_TGT_EMP should be Target
Mapping > TGT_EMP should be  Target

Result:

Please post your comments.