In an information processing system including a file shared by computer systems each having a central processing system and a main memory, a method for controlling access to the shared file includes a step of storing blocks read from the file into the main memory when the blocks of the file are updated, and a step of comparing at least a portion of the blocks held in a cache memory with at least a portion of the blocks stored in the main memory. When the comparison of at least the portion of the blocks held in the cache memory with at least the portion of the blocks stored in the main memory indicates mismatching, the block is read from the file into the main memory, and when the comparison indicates matching, the block of the main memory is updated. The data to be updated may be in a resident area, an input/output buffer or a same area.
Using the accumulated magnetic tape statistics in a storage medium (Sumlog File) which were retrieved from the unloading of specifically selected magnetic tape media, of a magnetic tape peripheral, a procedure is instituted to take the tape statistics through a Log Analyzer unit to analyze certain pages of data which then is fed to a Jobformatter unit which organizes each page of data into Write errors, Read errors, and other tape statistics returned by the tape peripheral. The Jobformatter sets-up a display of this information onto a display terminal or a printer.
A data processor is configured so that a mismatching does not occur between inputted or outputted data and data stored in a cache buffer region even when data is inputted or outputted by an application program to/from a block type device by bypassing the cache buffer region. A mismatched state eliminating unit is provided for copying data between the buffer for the application program to eliminate the mismatching when the mismatching results between the actually inputted or outputted data and the data stored in the cache buffer region. A selection condition holding unit is provided for holding a selection condition which determines whether or not to bypass the cache buffer region. An arbitrary value can be set in the selection condition holding unit by the application program. The block type device may comprise a flexible disk unit, a hard disk unit, or an optomagnetic disk unit.
In a buffer asynchronous output apparatus comprising a plurality of renewal processing programs each of which renews one of buffer areas in a system shared buffer unit as a renewed buffer area, a copied buffer area securing section secures a copied buffer area. A renewed buffer area copying section copies contents of the renewed buffer area into the copied buffer area. An output request enqueuing section enqueues an output request into an output request waiting queue. Performed asynchronously with the renewal processing programs, an output processing program comprises a file outputting section for outputting contents of the copied buffer area into a file device on reception of the output request dequeued from the output request waiting queue. After completion of a file output processing by means of the file outputting section, an output completion informing section stores an output completion status and a file output result status in a copied buffer information field on a buffer control table. In place of the copied buffer area securing section, an alternate copied buffer area securing section secures an alternate copied buffer area. A copied buffer area releasing section releases the copied buffer area. On ending of each of the renewal processing programs, a file output checking section checks whether or not the file output processing normally ends.
In a computer system including a disk subsystem having channel interface compatible to a count-key-data format and a SCSI interface compatible to a fixed length data format, the disk subsystem is connected to a CPU controlled by an open system operating system through the SCSI interface, and connected to an other CPU controlled by a main frame operating system through the channel interface. The CPU is provided with a CKD record access library and a VSAM access library which accesses in a FBA format the VSAM record stored by the other CPU in a CKD format in the disk subsystem and allows the access by an application program of the CPU as a VSAM record based on VSAM control information.
A shared fixed block architecture direct access storage system and method for use with a plurality of computer systems is described. The storage system includes a shared fixed block architecture direct access storage device with a plurality of shared files. A shared fixed block architecture control unit is coupled to the shared fixed block architecture direct access storage device and to the plurality of computer systems. The shared fixed block architecture control unit also includes a data unit responsible for moving data between a shared fixed block architecture direct access storage device in the computer systems, a SETL unit responsible for processing access requests and for creating control files corresponding to each shared file, and a heart beat unit responsible for updating the control files. The method of the present invention includes the steps of receiving an access request from one of the computers for access to a selected shared file; and if a control file corresponding to this selected file has not been previously created, then creating a control file corresponding to this selected file. The control file is read to determine if it contains a record indicating that another of the computer systems already has access to a selected file and whether that access is incompatible with the current access request. Finally, if either no other system currently has access to the requested file or if another system has access to the requested file which is not incompatible, then the access request is granted.
