How to check semaphores in Linux/ Unix? How to display semaphores in Linux/ Unix? How to view semaphores in Linux/ Unix?
Semaphores are used to access to shared system resources. They act as gatekeepers to ensure that particular shared system resources are not accessible by multiple processes at the same time. Oracle Databases use semaphores to manage access to operating system resources such as shared memory.
Display Semaphores Existing Values
When we install Oracle Documentation, it recommends to set semaphores to some values, so before modifying semaphores values, we must check semaphores parameters.
To view the semaphores information, you need to display the contents of /proc/sys/kernel/sem file. Below is the example is given to view the semaphores data using cat command:
$ cat /proc/sys/kernel/sem
340 44000 300 234
You can see above that there are four values which represent the following four semaphores kernel values:
semmsl - Maximum number of semaphores per set
semmns - Maximum number of semaphores on the entire system
semopm - Maximum operations for semop system call
semmni - Maximum number of semaphore arrays on the whole system