Not always I/O-related. Sometimes CPU-related but where SQL tuning would be more appropriate than application code instruction cycle tuning.
Cheers, Martin Martin Packer, Mainframe Performance Consultant, zChampion Worldwide Banking Center of Excellence, IBM +44-7802-245-584 email: [email protected] Twitter / Facebook IDs: MartinPacker Blog: https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker From: John Gilmore <[email protected]> To: [email protected], Date: 13/01/2012 13:20 Subject: Re: How bad is the EX instruction? Sent by: IBM Mainframe Assembler List <[email protected]> Gerhard Postpischil wrote: <begin snippet> In general I tend to agree with this, but I've worked or consulted at installations that either had problems completing overnight jobs in their assigned batch window, or just processing large amounts of data. </end snippet> I value GP's concurrence. Let me add, however, that 1) in my experience batch-window problems are always i/o-related; and 2) the unwashed always attack them in the wrong way, devoting resources to "optimizing" instruction sequences that, even if it had been possible to reduce their CP consumption to zero, would have left the batch-window problem unresolved. These applications, like most commercial batch ones, were i/o-bound, and their resolution required the use of overlapped, asynchronous i/o, which, for those who know how to do it, is not difficult. What it was/is in most of these shops was/is, quite literally, unthinkable. (The RESIDENCE time of a classical MFU can always be cut by a factor of four or more using asynchronous i/o.) John Gilmore, Ashland, MA 01721 - USA Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
