Messages on Q     (Overview)

DESCRIPTION
Sun MTP uses many system queues to communicate between Server components. A queue 
is an operating system resource enabling interprocess communication. Messages 
are posted on a queue by one process for retrieval by other processes. The 
"Messages on Q" datapoint applies only to the queue used for new transactions 
that have not been initiated yet. A Transaction Server pulls a request from this
queue as the Server becomes free.


VALUES
This datapoint is a number from 0 on up. 


INTERPRETATION

Operating system configuration controls the maximum number of messages allowed 
on a queue. The kernel parameters involved with the queue facility are usually 
called MSGTQL, MSGSEG, and MSGMNI. Refer to the Sun MTP Administrator's Guide 
for more information on how to set these parameters to accommodate a Sun MTP 
environment.

When this datapoint hovers around zero, either no transactions are taking place
or the Transaction Servers are keeping up with user requests. When this 
datapoint remains consistently high, or continues to grow, the Transaction 
Servers are not able to handle the number of requests.


CONCLUSIONS
When this datapoint stays at or close to zero for long periods of time, consider
reducing the number of Transaction Servers to free up memory and reduce CPU
contention. A Transaction Server sleeps when it has nothing to do. The operating
system wakes up all Transaction Servers when a transaction gets onto the queue, 
even when only one request gets put on the queue. Therefore, having too many 
Servers means too many processes are time-slicing for no reason.

When this datapoint is consistently high, or continues to grow, try slowly 
increasing the number of Transaction Servers. There may be too much work for
the current configuration. As long as there aren't any other problems, an 
additional Server might help get requests off the queue faster.

When the "Messages on Q" seems to freeze at a relatively high value, confirm 
server gridlock by examining the runtime statistics for the Transaction Servers 
in the Overview Screen's KxScrolledList. When the Servers keep the same 
statistics for a prolonged period of time, the system has hung. The most 
probable hang condition occurs when one of the kernel message parameters (see 
above) reaches the configured limit.

You might also consider whether or not you have enough CPU, memory, and/or swap 
space on your system to handle the requirements of your Sun MTP region(s). If 
you have a system monitoring tool, take a look to see if any of these areas are
being pushed to the limit. 
