I'm guessing that Peter was warning against the situation where you have an element table rather than a queue. Queues are straight forward because each entry will only be in use by 1 program at any given time (ownership is always the task using it). Element tables on the other hand may have multiple tasks referencing the same entry at the same time. An example that is easily understood is dynamic LPA. These modules exist in common storage and you may dynamically replace them with a new version. Anyone still using the old version must not abend so IBM leaves all old versions in storage until the next IPL. Since you don't know if anyone is using the old version, you can't free / reuse it. In the old days when CSA was constrained, it was a real problem to use such commands. Today, we don't think twice about it but it still eats up some CSA.
As for handling a queue, I use CS with the entries LIFO on the queue. A common task removes the queued entries and takes ownership. At that time, it repairs the forward pointers and gets the first entry. I haven't heard anything here that would make me think that PLO would be less expensive so I wouldn't bother changing it's implementation Jon Perryman. >________________________________ > From: Kenneth Wilkerson <[email protected]> > > > >Yes, I was talking about all references using PLO. I was also assuming this >was a "work" queue where "deletion" from the chain was the methodology for >claiming ownership of the element. > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
