process for dynamic extension of the assignment of a / ausgabegeraeten in a data processing system

摘要

1377110 Data processing systems INTERNATIONAL BUSINESS MACHINES CORP 10 Oct 1972 [16 Dec 1971] 46551/72 Heading G4A In a data processing system of the kind in which access to a resource is obtained by referring to a table of identifiers to resources maintained in the system, provision is made for dynamically extending a resource allocated to a task, after initiation of that task, by adjusting the table relative to that resource. The invention is described as an addition to the IBM (Registered Trade Mark), System 360-370 operating system. An additional I/O unit required for a task is defined in terms of its class and device type, and control blocks (UCB) of which one exists for each I/O device in the system, are searched until one is found for the appropriate class and type of device on which the "volume" containing a specified data set to be accessed is or can be mounted. If a unit having the specified volume mounted thereon is not found by searching the UCB's, an appropriate unit without a mounted volume or with a dismountable volume which is not designated as retained or having passed data sets, or with another dismountable volume, is allocated to the task in that order of preference. When, during the execution of a task, the end of a first volume is reached, information specifying the volume number and device class and type of a volume added to the data set after initiation of the task, is looked up and the UCB's are searched for an appropriate I/O unit as above.