I'm confused. If a program is reading or writing a dataset sequentially, then it does so one I/O (block) at a time.
If another program is concurrently reading, then it will be doing I/O's more or less concurrently and the likelihood of cache hits rise. If you are writing, you write only one block at a time. With 'fast write', the operation ends once the block is in the device cache. What happens physically is not that relevant. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of McKown, John Sent: Wednesday, April 09, 2008 10:42 AM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Sequential Data Striping There is one left. Even if the data is physically striped on the DASD, when you read an unstriped, in z/OS's view, disk dataset, you do a single I/O operation. If you use z/OS striping, you do multiple I/Os (one to each stripe), which hopefully means that you wait less for the I/O operation. The same on a write. I.e. the amount of data concurrently transferred is greater. Of course, if you have my luck, each stripe (z/OS DASD volume) will end up being on the same physical back end DASD and nothing will be prefetched in cache either. "If it weren't for bad luck, I'd have no luck at all." -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology NOTICE: This electronic mail message and any files transmitted with it are intended exclusively for the individual or entity to which it is addressed. The message, together with any attachment, may contain confidential and/or privileged information. Any unauthorized review, use, printing, saving, copying, disclosure or distribution is strictly prohibited. If you have received this message in error, please immediately advise the sender by reply email and delete all copies. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
