Java Heap Space Error (Elastic cluster or Client application)

I have an application that sends too many queries to ELS (elastic search) cluster (both search and multi-search and sometimes scroll). I use java transport client for connection. Now I am getting this into the logfile of my application

[elasticsearch[client][transport_client_boss][T#12]][AbstractChannelHandlerContext:149] An exception 'java.lang.OutOfMemoryError: Java heap space' [enable DEBUG level for full stacktrace] was thrown by a user handler's exceptionCaught() method while handling the following exception:
java.lang.OutOfMemoryError: Java heap space

I have some questions:

  • this "Java Heap Space" happens in the ELS cluster or in my own application
  • where does this T#12 belong to? (ELS or my java application)

Thanks in advance