Semaphores

Hi, Can you please clarify my below doubts?. 1. What is Semaphore in Informix and what's the use of this? 2. How many Semaphores can be reside in an Informix - server? Thanks in Advance. Regards, Ravi Shankar N.

Semaphores are not generally used in IDS for locking purposes because of the multi-threaded aspect of IDS. Instead semaphores are used to place the VP in a blocked state when that process has nothing to do. That means that there is one semaphore for each VP. Additionally, there are two semaphores used for each IPCSHM poll thread. One to protect the IPCSHM memory buffers and the other to act as a signal between the client and the poll thread. Also there is a semaphore allocated for each client using IPCSHM that the client will sleep on after passing a message to the engine and while it is waiting for a response from the engine. N.B. Since we allocate semaphore arrays rather than individual semaphores, you will not see a seperate entry for each semaphore in the 'ipcs' command. M.P. "N Ravishank...." <W2925C@motorola. To: ids@iiug.org com> cc: Sent by: Subject: Semaphores [1782] forum.subscriber@ iiug.org 09/02/2003 05:48 AM Hi, Can you please clarify my below doubts?. 1. What is Semaphore in Informix and what's the use of this? 2. How many Semaphores can be reside in an Informix - server? Thanks in Advance. Regards, Ravi Shankar N.