No. However, while there is no designed limitation to the size of a ToolTalk message or the number of arguments ToolTalk does copy the data several times (both from one area in the client's address space to another area, and across the RPC connection to and from the server). For example, a megabyte of data in a ToolTalk message would be copied at least 4 times:
From your storage to the ToolTalk library's storage
From the ToolTalk library to the ToolTalk server
From the ToolTalk server to the receiver's library
From the receiver's library to the final resting place.
If there are processes observing the message, even more copying will take place. In addition, no other messages for this session can be delivered during the copy time because the ttsession process is single-threaded. Therefore, if you plan to send really big chunks of data very often, you probably want to consider using a non-ToolTalk way to pass the data.