using multiple parameter files in informatica

You must follow below steps, or you will be failed.

Workflow and Session Level Parameter File

When we define a workflow parameter file and a session parameter file for a session within the workflow, the Integration Service uses the workflow parameter file, and ignores the session parameter file. What if we want to read some parameters from Parameter
file at Workflow level and some defined at Session Level parameter file.

The solution is simple:

Define Workflow Parameter file. Say infa_shared/BWParam/param_global.txt
Define Workflow Variable and assign its value in param_global.txt with the session level param file name. Say $$var_param_file=/infa_shared/BWParam/param_runtime.txt
In the session properties for the session, set the parameter file name to this workflow variable.
Add $PMMergeSessParamFile=TRUE in the Workflow level Parameter file.

Content of infa_shared/BWParam/param_global.txt (Workflow Parameter file)

[WorkFolder.WF:wf_runtime_param]
$DBConnection_SRC=Info_Src_Conn
$DBConnection_TGT=Info_Tgt_Conn
$PMMergeSessParamFile=TRUE
$$var_param_file=infa_shared/BWParam/param_runtime.txt

Content of infa_shared/BWParam/param_runtime.txt (session parameter file )

[WorkFolder.wf:wf_runtime_param.ST:s_m_emp_cdc]
$$start_date=2010-11-02
$$end_date=2010-12-08

The $PMMergeSessParamFile property causes the Integration Service to read both the session and workflow parameter files.

http://dwbi.org/etl/informatica/150-stop-hardcoding-follow-parameterization-technique