.fo left .sp Date: June 19, 1986 To: John B. Lohmeyer, X3T9.2 Chair NCR Corporation Wichita, Kansas From: Gary R. Stephens IBM Corporation Tucson, Arizona Subject: MOSE SELECT Changes Causing a Unit Attention Condition for Tape Devices I have checked all of the options in the MODE SELECT command and I can find no conditions other than those listed in the UNIT ATTENTION section of the standard that requires setting a unit attention condition. Volume removal and reset are the only two conditions which should cause this conditon. Initiators are permitted, when a target is not reserved, to perform all operations. Synchronization of changes of format, location, and partition must be assumed to be coordinated outside the target. A MODE SELECT command to change the format, when positioned at load point, is not actually performed unless a write operation is performed. A change of format, potentially established upon successful completion of the MODE SELECT command, cannot cause a unit attention condition since it is not truly effective until some later write-type command is executed. A disk format change would alter the application set which can use the device. A tape format change usually only affects the speed at which future operations are executed. Gary R. Stephens