Keep in mind that your application will be dreadfully slow and simply will not scale. Even with modern DASD with response times in the sub millisecond range.
Consider that each logical write may drive several physical operations. Ask your DASD czar what the unit response times are, and do the math. Just picking numbers out of the air: suppose that one 'transaction' drives four I/O operations. Each of those drives five alternate index operations. That's 20 synchronous I/O's. (Just guessing about the numbers. One write to a KSDS would include the target record plus the index record. There may be a couple more operations updating various pointers within the cluster. Each AIX would carry its own overhead.) DASD performance numbers are an average. You can achieve sub millisecond response times only with very aggressive buffering and caching. Without such, you might reasonably expect times in the half second range. It might be hard to explain a ten second response time to the average user. Not to mention an absolute cap of six transactions per minute. Things get exponentially worse as you add users. So, IMNSHO, synchronous I/O is not a good way to win the hearts of your users and please your management. HTH and good luck. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Arie Kremer Sent: Sunday, February 25, 2007 10:43 AM To: [email protected] Subject: KSDS immedial write Hi, could I define KSDS cluster so that each update (I use C code with assembler routines) will put to DASD immediately? I'd like to use it as a pseudo log file. The cluster has to have alternate indexes. As far as I know, fflush() does not work with VSAM. Arie Kremer 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
