MAXACCESSSERS

Equals the number of semaphores.

Number of message queues is almost equal to MAXACCESSERS + number of servers with reply queues (number of servers in MSSQ set * number of MSSQ sets).

MAXSERVERS, MAXSERVICES, and MAXGTT

While MAXSERVERS, MAXSERVICES, MAXGTT, and the overall size of the ROUTING, GROUP, and NETWORK sections affect the size of shared memory, an attempt to devise formulas that correlate these parameters can become complex. Instead, simply run tmboot -c or tmloadcf -c to calculate the minimum IPC resource requirements for your application.

Queue-related kernel parameters

Need to be tuned to manage the flow of buffer traffic between clients and servers. The maximum total size (in bytes) of a queue must be large enough to handle the largest message in the application. A typical queue is not more than 75 to 85 percent full. Using a smaller percentage of a queue is wasteful; using a larger percentage causes message sends to block too frequently.

Set the maximum size for a message to handle the largest buffer that the application sends.

The maximum queue length (the largest number of messages that are allowed to sit on a queue at once) must be adequate for the application's operations.

Simulate or run the application to measure the average fullness of a queue or its average length. This process may require a lot of trial and error; you may need to estimate values for your tunables before running the application, and then adjust them after running under performance analysis.

For a large system, analyze the effects of parameter settings on the size of the operating system kernel. If they are unacceptable, reduce the number of application processes or distribute the application across more machines to reduce MAXACCESSERS.