Abstract: Count, key, data (CKD) datas are stored on fixed block (FBA) disk recorders (DASD). A virtual track is created which emulates a physical CKD track such that the byte displacement of each CKD record on the virtual CKD track is the same as the byte displacement would be on a physical CKD track. This enables computer programs using CKD formatted data to record on the FBA recorder in an emulation mode. Each FBA block includes a header outside the addressing of the virtual CKD track which includes a byte displacement pointer to the beginning of a first CKD record stored in the FBA block, if any begins in such FBA block; otherwise the header indicates that no CKD record begins in the block. A last record indicator is included in the count field emula-tion for assisting in finding end of the virtual track.

Abstract: A state of operation is established in accordance with rules for a peripheral subsystem which enables reduced channel time for executing ensuing related channel commands of the same channel program. In a peripheral data-storage subsystem, a set of rules of operation are established. Each rule sets forth a predetermined set of sequences of channel commands during any chain of channel commands (channel program) which predict ensuing channel operations in channel program currently being executed. Once any rule is satisfied, a state of operation is established in the subsystem for responding to ensuing channel commands in the same channel program and which relate to the channel commands set forth in the rules. So long as such related ensuing channel commands continue or until the end of the channel program the state of operation is maintained in the subsystem.