After a message is ended (by using the MESSAGE END statement) and is committed (to make it persistent), you send it to the master database by using the MESSAGE FORWARD statement, see MESSAGE FORWARD.
Each sent message receives a reply message from the master database and each message returns a result set that should be fetched by the client application.
For example:
MESSAGE mymsg FORWARD TIMEOUT 60;
You can set the TIMEOUT option to define how long the replica database waits for the reply message before it expires or you can specifically request a reply by using the MESSAGE GET REPLY statement, see Requesting a reply message from the master database.
Note If a master database does not receive a complete message, none of the message is processed.