In a message dated 1/16/2007 6:19:54 P.M. Central Standard Time, [EMAIL PROTECTED] writes:
>Unit Check means that you need to issue a SENSE command to determine >the type of event. A more accurate way to say this is that Unit Check means that the sense data needs to be examined. For maybe 10 years now at least IBM DASD controllers have been sending the full set of sense data into central storage along with the status at the time of the interrupt. This feature, called Concurrent Sense, allows IOS not to have to incur the overhead and time delay of doing a separate I/O in order to read sense data. The sense bytes are stored in the extended control word within the IRB. There is a bit in the SCHIB that indicates whether or not the device presents sense data concurrently with the normal interrupt data such as status. I am not sure which device-related control block in storage has this same info. These sense bytes are only sent into central storage if the status includes unit check. Bill Fairchild ---------------------------------------------------------------------- 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
