Bill, My understanding (could be completely wrong, which is why I'm asking the question) is....
XRC will block a primary volume for a certain amount of time (the time the device is blocked is dependent on the vendor) if XRC can't keep up with the records that need to be written to the secondary volume. If the residuals go above a certain threshold (x'500' at our site)then XRC blocks any I/O to primary volume (unless specified as DONOTBLOCK). It has never been explained to me exactly how this happens. If I could find it in a manual (believe me, i've tried), I'd be a happy Storage Administrator. Bear in mind that XRC is Asynchronous. I can see that PPRC and synchronous copy delays are recorded in DISC time, but it says nothing about Asynchronous delays. The CMR is the Command Response from the CU to the IOS to say that it was ready for the I/O? I understood that until the CMR is recieved, the SSCH command is not issued. If the device blocking stops the CU from issueing a CMR, then IOSQ time would be where the delays are recorded as the SSCH hasn't been issued. Please feel free to pull my understanding to pieces as it's only through fully understanding what is happening that I can get to grips with the process and find out where our problems lay (lie?). Our performance team are saying that XRC device blocking is causing the problems as can be seen by the high DISC times. I don't believe that explanation (but am willing to eat humble pie if they're right and I'm wrong). JJ ---------------------------------------------------------------------- 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
