In my bpel there is a variable whose payload size is more then 5 mb so after use this variable I want to make this variable empty. Can someone suggest how can I achieve this.
You could limit the variable's usage by placing it in a relatively small scope. if its a local variable it will only be active inside it's scope. If your whole BPEL consists of a single scope, you might run into memory problems. If you scope wisely, you might not :). Limit the scope to the components of the BPEL actually using the variables inside it.
I hope this helps!
Jesper