Ted, There may be a statistical impact on DASD response time, but I don't believe that mirroring page datasets actually impacts performance to any significant degree. Page in of any variety is not affected by Synchronous remote copy. It's a read and reads are local. Most page ins are synchronous to task execution and thus this performance stays the same.
Page outs are not synchronous to task execution. As I read it most page out activity is related to low touch pages and tasks are unaware that the page has even moved to AUX until it needs to page it in again. Whether the page out takes 0.5ms or 1.5ms with Synchronous Remote Copy does not really affect performance, just performance statistics. The only impact would be Memory challenged environments that require expeditious page out performance to make room for spikes in memory usage, where the source of the spike is mission critical. The reason I don't mirror page datasets is that any reduction in link traffic is a good reduction. It goes hand in hand with "the best IO is the one you don't do." With page out rates as low as we see today and the big pipes used for Synchronous remote copy I have to consider if this rule is still valid. XRC, HUR and TrueCopy Asynch have other challenges with paging because of timestamps. I recommend Skip's technique for these products. Ron > > If it's synchronous double the I/O response. > If it's also to another site --GDPS-- add in the speed of light > differential. > > Also, at a second site, none of the data will be used. > It will be the virtual/real storage map of the second site. > > - > Too busy driving to stop for gas! > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- 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
