Agreed, a 50% hit rate is pretty bad, but a heck of a lot better than zero.
If you could somehow exclude the file from all caching, then I would expect a drastic degradation of I/O performance. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of jason to Sent: Tuesday, February 17, 2009 5:59 PM To: [email protected] Subject: High DASD disconnect time due to RANDOM READ I have discovered we have been experiencing high disconnect time to most our LCUs/DASDs due to NORMAL/RANDOM read CACHE misses (only 50% hit ratio). I have read somewhere that NORMAL read normally is not recommended for CACHING and was suggested to be excluded. My question is have anyone here implemented this to exclude the NORMAL read thru SMS storage class? After the exclusion, does it really improve the IO performance? how to handle those files both have normal/sequential read? TIA. Regards, Jason ---------------------------------------------------------------------- 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 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
