Can someone help me on how to execute a step in a JCL on a conditional basis..
Condition should be if the flat file exists, then execute the step. That is only if the flat file is present, then the step should be executed. I know there is an option called "LISTCAT". But my file uses symbolic parameters.
It would be of great help if someone posts that conditional part alone.
JCL conditionals cannot be used to determine file existence. As stated, your request cannot be implemented. You can generate a LISTCAT, parse the output with a utility or a program YOU write, then submit a second JCL depending upon whether or not the file exists. However, you cannot do all this in a single job -- you MUST submit a second job that can include or exclude the step you don't want to run if the file doesn't exist.
Learn to use the search function. This topic has been discussed many times on this forum and if you searched the forum before posting you would have answered your question already.