RE: Semaphor

["Elvis Budimlic" <ebudimlic@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Semaphore is inter-process synchronization object popular on other platforms
and is finding its way to System i world via cross-platform ERP applications
and programmers.
It can be used for locking purposes, much like mutex or object lock.  It can
also be used for resource accounting.  It's simply an integer value in an
array of integers (semaphore set).  It can have a max value, so say when you
only want 7 people to print to the printer, you can set the max value to 7
so next time your application requests a semaphore it'll have to wait until
one of those original 7 releases its own handle (decrements integer count by
1).
So, it's purely a synchronization object used by application programmers.
It has its use and is very nice mechanism when used appropriately by the
developer.  When not, bad things happen (i.e. requests back up).

I've seen some of these issues occasionally with one ERP solution and is
usually caused by administrators running multiple tasks that conflicted with
each other.

<vendor plug>
We've developed a tool that lets you look at jobs in SEMW (semaphore wait)
state and get all the details you'll need on it (like who posted to it last
- i.e. who didn't post back and release the 'lock').  It'll even let you
post the waited on value to the semaphore, in effect releasing your job, but
I don't usually recommend it unless it's an emergency and you'll get fired
unless backed up job runs :)  
Better course of action is informing developer of the conflict and
presenting him with all the information found so he can diagnose the issue
within the application.

http://www.centerfieldtechnology.com/tools/lockdetector.asp

This function is part of insure/MONITOR tool.
<unplug>

Elvis

-----Original Message-----
Subject: Semaphor

I have never heard of Semaphor, but apparently was having problems with it
last week. What is it? Is there another way to clear it out (or reset or
whatever) besides an IPL?

--
Mike Wills
koldark@xxxxxxxxx
http://mikewills.name
http://theriverbendpodcast.com