Bmc Software, Inc.

William R Cunningham

Linda S Ball

Thomas G Price

Stanley James Dee

Michael L Perry

Thomas E Hintz

Carla C Birk

Shawn B Wikle

Techniques to provide run-time access to a database image through a target database management system (DBMS) are described. An empty database in the target DBMS (the 'target database') is created having substantially the same schema as the database image. At run-time, queries directed to the target database are intercepted and redirected to the database image. Information returned in response to the redirected query is modified so that internal database identifiers retrieved from the database image are replaced with like database identifiers associated with the target database management system. Thus, run-time access to database image content is provided without the need to load the database image's data content into a target database.

Run-time access techniques for database images

A computer program operating in accordance with the invention monitors WRITE requests issued by a data-writing program that accesses data sets, e.g., for updating the data sets, and READ requests issued by a data-reading program that accesses data sets, e.g., for copying the data. While a series of READ requests (e.g., a data set copying operation) is in progress, the computer program monitors all WRITE requests issued for the data set in question by the data-writing program. If the data-reading program has not yet read the data portion (e.g., a data page) that is to be updated, the computer program selectively creates a cached image of the data portion as it existed at the beginning of the series of READ requests and delivers the cached image to the data-reading program, thereby reducing the potential for internal inconsistencies in the copied data. The computer program advantageously permits such caching to be performed without the need for specialized caching hardware.

Method of creating an internally consistent copy of an actively updated data set without specialized caching hardware

A method of caching I/O requests permits caching in the MVS environment independent of the access method protocol used to initiate an I/O request (e.g., QSAM, VSAM, Media Manager). In addition, objects can be user-prioritized for residence in the cache.

Method of avoiding physical I/O via caching with prioritized LRU

The reorganization method of DB2 data files explores parallel processing, and asynchronous I/O to a great extent. It includes means to estimate an optimum configuration of system resources, such as storage devices (DASD devices), memory, and CPUs, etc, during reorganizations. The method mainly consists of four components, (1) concurrent indexing, (2) concurrent unloading of data file partitions, (3) efficient reloading of DB2 data pages and DB2 space maps, and (4) means to reduce access constraints to the DB2 recovery table.

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Austin, TX, United States of America

William R Cunningham