Hi - If you check the documentation links already provided, you will notice that the only new DCMT commands for 19.0 are DCMT to:
1- dynamically vary zip off and on
2- vary the log.
DCMT Vary zIIP dynamically enables/disables the IDMS system from using the zIIP processor. The zIIP processor can only be varied if the SYSTEM is brought up with ZIIP=Y. For more information on this command, see System Tasks and Operator Commands.
DCMT Vary Log calls the WTOEXIT user exit to offload the Log. For more information about how this address is generated, see System Tasks and Operator Commands.)
I hope this additional detail is helpful. - Cal Domingue, CA Principal Support Engineer