This FM can be used to send a quick message to another user on any system in the landscape. This can be used when other users are locking certain transactions and not releasing them for a long time. Here are the steps. However, please use this judiciously and do NOT spam other users when not required.
Step 1 : Go to Txn [ SE37 ] .
Step 3 : Enter the client Number ( In our case its 800 , since this is an IDES client ) , user id that has locked your Txn and the Message. An example is shown below.
Result : The targeted user gets the message as shown below as a pop-up .