Q????

What does Q mean again. I forgot and I'm getting an eerror that reads

OSLR mqsend Q overflow

I can't seems to figure this error out

I'm no expert in communications or digital buffers, but I think that in this case "Q" is short for "queue" (pronounced "cue"), which has various meanings. In electronics, it means a buffer like a FIFO (first-in, first-out memory). If more data comes in than the buffer can handle, it overflows.
Look up the definition of "queue" on Google.