Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1998-09-25
2001-02-13
Alam, Hosain T. (Department: 2771)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C711S101000, C711S202000
Reexamination Certificate
active
06189015
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the field of data storage. More particularly, this invention pertains to a method and apparatus for updating the control information of a non-VSAM data set for data that is not read into the host during transfer.
BACKGROUND OF THE INVENTION
One of the key components of a computer system is a place to store data. Typically computer systems employ a number of storage means, including “volumes” which can be disk drives (also called a direct access storage device or DASD), that are used to store data. Physical volume storage systems typically employ some number of physical volumes that each contains multiple tracks on which to store data.
An alternative to a physical volume storage system is a virtual volume storage system. A virtual storage system, such as a log-structure array system, typically contains a number of “virtual volumes,” each having a “virtual track table” with pointers to “virtual tracks” on the virtual volume. The description of a virtual storage system is contained in IBM publication “IBM RAMAC Virtual Array” document no. SG24-4951-00 (IBM Copyright, 1997) which is incorporated herein by reference.
Both VSAM and non-VSAM data sets can be stored in a data storage system. Non-VSAM data sets differ from VSAM data sets in their organization and control information. The present invention is directed to maintenance of control information during data movement of non-VSAM data sets.
Data movement involves the copying and/or moving of a data set from one volume or set of volumes to another volume or set of volumes within a storage system. As the data set is copied or moved, the layout of the volumes within that storage system changes. However, even after a movement of the data set, the control information for the target data set that has been copied or moved must be maintained.
Unlike a physical volume environment, in a virtual volume environment the data set is not read into a host when the data set is moved. Within a virtual volume storage system, it becomes very difficult to maintain the control information when moving non-VSAM data sets that are not read into the host. Therefore, it becomes very difficult, or impossible, to determine the amount of data that actually resides on each volume after movement of non-VSAM data sets that are not read into a host computer.
SUMMARY OF THE INVENTION
The present invention provides an improved data set control information tracking system and method that substantially eliminates or reduces disadvantages and problems associated with previously developed systems and methods used for maintenance of non-VSAM data set control information.
More specifically, the present invention provides a system and method for maintaining non-VSAM data set control information when moving a data set from a source volume to a target volume. From the control information on the source volume(s), the total space or number of tracks required to store the data set is determined and at least that amount of space is allocated on the target volume(s). The data set is moved to the target volume without reading the data into a host computer. A data movement program will compare the space allotted for the data set in each target volume to the total size of the data set to determine if the data set filled each target volume. In one embodiment, to determine the control information for the last target volume with data from the data set, the data movement program will subtract from the total number of tracks of data in the data set the number of tracks of data stored in previous target volumes to determine the number of tracks on the last target volume. The data movement program will combine this number of tracks with the number of records on the last track of the source volume to give the control information for the data set on the last target volume.
The present invention provides an important technical advantage by maintaining non-VSAM data set control information after movement of the data set from a source to a target volume.
The present invention provides another technical advantage by allowing the determination of the beginning and ending points on a target volume of a non-VSAM data set after movement from a source volume.
The present invention provides yet another technical advantage by maintaining control information for a non-VSAM data set after movement in both physical and virtual storage system environments.
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Reed David Charles
Thompson John Glenn
Alam Hosain T.
Dan Hubert & Assoc.
International Business Machines - Corporation
Ly Anh
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