In a message dated 12/17/2007 11:08:27 A.M. Central Standard Time, [EMAIL PROTECTED] writes: >I was under the impression that the access methods (e.g., BSAM, QSAM, etc.) used EXCPVR rather than STARTIO. Is that not the case? That is not the case. QSAM, BSAM, BPAM, and BDAM all use EXCP inside the access methods when it is necessary to do the I/O. EXCP in turn uses STARTIO. IOS was redesigned when MVS was spawned from MVT. In OS/360, the lowest level access method was EXCP. MVS added a new lower level, STARTIO, which in turn is used by what are called IOS Drivers. Look in the IOSB DSECT for the field IOSDVRID to see all the various IOS Drivers which IBM has documented as existing via IOSDVRID. There may be others. >But, often necessary. Currently, STARTIO is the only I/O interface offered by z/OS that can be used in SRB mode. Which is because all the other interfaces use an SVC, which is illegal in SRB mode. STARTIO uses a BALR. Also STARTIO can be used to "schedule" an I/O request even when running disabled. Bill Fairchild Franklin, TN
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