Every process that participates in an Oracle Tuxedo application requires a semaphore. A semaphore is a hardware or software flag used to prevent processes from accessing the same shared memory space at the same time. When a process has control of a shared memory resource, all other processes are locked out of the shared memory resource until the process releases the resource. When the Oracle Tuxedo application is booted, the underlying Oracle Tuxedo system checks the number of semaphores configured in the operating system. If the configured number is not high enough, the boot fails.

The following semaphore parameters may need to be adjusted:

SEMMNS

Maximum number of semaphores in the system. The minimum requirement for SEMMNS is MAXACCESSERS - MAXWSCLIENTS + 13, where MAXACCESSERS is the maximum number of Oracle Tuxedo system processes on a particular machine (including servers and native clients) and MAXWSCLIENTS is the maximum number of Oracle Tuxedo remote clients. Both of these parameters are specified in the UBBCONFIG file for the application. For more information about UBBCONFIG, see Creating the Configuration File or UBBCONFIG(5) in the File Formats, Data Descriptions, MIBs, and System Processes Reference.

SEMMNI

Maximum number of active semaphore sets.

SEMMSL

Maximum number of semaphores per semaphore set. SEMMNI andSEMMSL are commonly chosen so that their product equals SEMMNS. The Oracle Tuxedo system does not perform semaphore operations on semaphore sets; however, it attempts to allocate as many semaphores per semaphore set as possible.

SEMMAP

Size of the control map used to manage semaphore sets. SEMMAP should be equal toSEMMNI.

SEMMNU

Number of undo structures in the system. Because an undo structure is needed for each process that can access the bulletin board, SEMMNU must be at least as large as SEMMNS. (The UNIX operating system uses undo structures to unlock semaphores held by processes that die unexpectedly.)

SEMUME

Maximum number of undo entries per undo structure. The value 1 suffices.