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Defining IPC Limits
Because most interprocess communication (IPC) and shared memory bulletin board tables are statically allocated for speedy processing, it is important to tune them correctly. If they are sized too generously, memory and IPC resources are wasted; if too small, processes fail when the limits are exceeded. You can use the tmloadcf -c command to find out the maximum IPC resources required by a specific application. (See tmloadcf(1) in BEA Tuxedo Command Reference.)
MAXACCESSERS, MAXSERVERS, and MAXSERVICES are the tunable parameters that control IPC sizing. The amount of shared memory allocated in an application is controlled by the MAXGTT and MAXCONV parameters.
Characteristics of MAXACCESSERS, MAXSERVERS, and MAXSERVICES Parameters
Note: Examples of system-supplied servers are AUTHSVR, TMQUEUE, TMQFORWARD, TMUSREVT, TMSYSEVT, TMS, TMS_QM, GWTDOMAIN, and WSL.
The cost incurred by increasing MAXACCESSERS is one additional semaphore per site per client or server process (accesser-see note that follows). There is a small fixed semaphore overhead for system processes in addition to that added by the MAXACCESSERS value. The cost of increasing MAXSERVERS and MAXSERVICES is a small amount of shared memory that is kept for each server, service, and client entry, respectively. The general idea for these parameters is to allow for future growth of the application. It is more important to scrutinize MAXACCESSERS.
Note: The system allocates one semaphore for each access slot to the bulletin board. A semaphore is a latch circuit that prevents more than one process from accessing the same shared memory in the bulletin board at the same time.
For BEA Tuxedo pre-Release 7.1 (6.5 or earlier), both the MAXACCESSERS and MAXSERVERS parameters for an application play a part in the user license checking scheme. Specifically, a machine is not allowed to boot if the number of MAXACCESSERS for that machine + the number of MAXACCESSERS for the machine (or machines) already running in the application is greater than the number of MAXSERVERS + user licenses for the application. Thus, the total number of MAXACCESSERS for an application must be less than or equal to the number of MAXSERVERS + user licenses for the application.
The user license checking scheme in BEA Tuxedo Release 7.1 or later considers only the following two factors when performing its checks: the number of user licenses for an application and the number of licenses currently in use for the application. When all user licenses are in use, no new clients are allowed to join the application.
Example Settings
*RESOURCES
MAXACCESSER 75
MAXSERVERS 40
MAXSERVICES 55
In this example, at most 75 processes (clients and servers) can access the system at any one time. There is room for 40 servers advertising 55 services in the bulletin board.
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