Performance issue using the UDF

Hi All,

We have bulk load jobs configured using SSIS packages. All the load jobs were working perfectly fine until 2 days back. Suddenly, our load jobs are taking way longer than the normal time. The issue is identified to be the use of UDF as shown below,

Note: These jobs were working fine since 3 years without any issues. We load around 16 GB of data each day.

No changes to the server and\or SQL Server itself.

Any help would be greatly appreciated.

Thanks,

-Mohsin

ALTER FUNCTION [dbo].[convertdate_null](@input varchar(50))     

RETURNSVARCHAR(12)     

AS    

BEGIN   

 DECLARE @outputDATETIME;   

 SELECT @output=CASE WHEN (ISDATE((CASEWHEN Left(replace(ltrim(rtrim(@input)),'+',''), 1)= 1         

          THEN'20'         

          ELSE'19'      

           END +Right(ltrim(rtrim(@input)), 6))   

          )= 1)     

      THENCONVERT(VARCHAR(12),CONVERT(DATETIME,CASEWHEN Left(replace(ltrim(rtrim(@input)),'+',''), 1)= 1         

             THEN'20'         

             ELSE'19'      

            END +Right(ltrim(rtrim(@input)), 6)) )    

      ELSE    

      null 

     END      

RETURN @output   

END