SYSIN concatenation is mostly used when you are running DB2 queries in batch. 
You have all the query ready except the input that USER provides, 
which needs to be used in the WHERE condition.

The USER data can be put in a dataset (HLQ.USER.DATA) and can be concatenated 
with rest of the query in SYSIN as shown below.

//SYSIN    DD *
  SELECT COL1, COL2, COL3
    FROM TABLE1
   WHERE COL0 =
//         DD DSN=HLQ.USER.DATA,DISP=SHR
//         DD *
     AND COL9 > 0
  ;