Semaphores are used to make system free from conflicts and
hang. when more than one program are executed
simultaniously then computer hangs and sometimes gives
wrong output so instead to come out from this situation
semaphore is used which takes care for program execution
and manages it.
semaphores is avariable which is used for restricting
access to shared resources.A semaphore contains a counter
for the number of available resources.Any process which
wants to access the resorse will first check the value of
On some UNIX® systems, the system administrator can edit
the /etc/master file and define limits for IPC mechanisms
(semaphores, shared memory segments, and message queues).
The problem with this method is that the higher the limits,
the more memory the operating system uses, and performance
can be adversely affected.
AIX uses a different method. In AIX®, upper limits are
defined for the IPC mechanisms, which are not configurable.
The individual IPC data structures are allocated and
deallocated as needed, so memory requirements depend on the
current system usage of IPC mechanisms.
Semaphores 4.3.0 4.3.1 4.3.2 5.1 5.2 5.3 6.1
Maximum number of semaphore IDs for 32-bit kernel 4096 4096
131072 131072 131072 131072 N/A
Maximum number of semaphore IDs for 64-bit kernel 4096 4096
131072 131072 131072 1048576 1048576
Maximum semaphores per semaphore ID 65535 65535 65535 65535
65535 65535 65535