International Business Machines Corporation

Gerald P Bozman

William H Tetzlaff

Robert Baird

James J Myers

Alexander S Lett

Jay H Unger

George Eisenberger

John Arthur Pershing, Jr

John Timothy Robinson

Paul Hodges

Richard Roland Guyette

Pong-sheng Wang

Nancy Y Young

Robert R Berbec

Thomas Beretvas

Joann Ruvolo-Chong

John J McAssey

Albert Kamerman

A computerized method, system and computer program product for managing an object store is disclosed. An exemplary method includes the the steps of: collecting performance statistics about storage repositories from which an object(s) can be retrieved; retrieving an object from a storage repository, in response to an object reference; determining a reference probability (RFP) for the object; determining and associating a replacement penalty (RPP) with the object wherein the RPP is based on the one or more performance statistics and the RFP; and storing the object and an associated RPP for the object. The storage repositories could be locally attached devices, network sites, and/or remotely attached devices. If there is insufficient space in the object store for a new object, an object(s) can be replaced with the new object based on the associated RPP of the cached objects. Alternatively, the resolution of one or more objects in the object store can be reduced until sufficient space is available. The RPP determination is preferably based on the RFP for the object and performance and/or usage statistics. Examples of the performance statistics include: availability; size; latency; and bandwidth. An example of the usage statistics includes statistics on time delays (D) associated with abort requests made via the Internet, for example, using a browser. The RPP could include an annoyance function for a specific requester or set of requesters by instrumenting the browser STOP function and analyzing time interval statistics associated with its usage.

Managing an object store based on object replacement penalties and reference probabilities

A method for dynamically detecting loss of map integrity in a form of system-managed storage (SMS). In SMS, maps are used to define access paths to data and to allocate and reallocate storage resources among applications running thereon. The method steps include incorporating as an indivisible part of an overwriting commmand the duplication of map information by appending a portion of it to each data block in store, and detecting loss of map integrity as a function of a comparison mismatch between the portion stored with a counterpart data block and the map upon each read/write access.

Method for verification and restoration of directories in CPU system

A computer implemented method for robustly copying pages to system managed storage in order to maintain data in a consistent state and in order to provide continuous access availability of the pages to executing applications. The method achieves data consistency by atomically shadow copying application referenced pages and amending directories in a failure independent medium on (1) an access path interrupt as well as on (2) a page update basis. Availability is enhanced by duplexing the pages and directories as part of the atomic shadow copying step.

Highly available fault tolerant relocation of storage with atomicity

A method and apparatus for providing non-privileged state cross-memory communications between application programs in disjoint communication memory domains. Appropriate operating systems store a table indicating which communication memory domains and which operations are permitted by a corresponding application program in a corresponding communication memory domain.

Problem state cross-memory communication using communication memory

A method for managing space re-use with respect to the indices (nodes) of shadow written tree organized dynamic random accessed files/records/pages located in the external store of a CPU. The method reserves space in all non-leaf nodes and maintains a list of available node addresses. When a new node is required then space, if available, is obtained from the parent node list. Only when the parent list becomes exhausted is space (node) obtained from a node inventory manager. Deletion of a node causes its address to be placed on the free or available list maintained by that node's parent. If there is no space, then space on the parent node list is obtained by returning to the inventory manager that node on the list having the least locality with the existing subordinate (children) nodes of the parent.

Managing locality in space reuse in a shadow written B-tree via interior

A conditional broadcast or notification facility of a global lock manager is utilized to both serialize access to pages stored in local caches of counterpart processors in a distributed system and to ensure consistency among pages common to the caches. Exclusive use locks are obtained in advance of all write operations. When a page is to be updated, which page is cached in a processor other than that of the requester, then a delay is posed to the grant of the exclusive lock, all shared use lock holders to the same page notified, local copies are invalidated, exclusive lock granted, page is updated and written through cache, after which the lock is demoted to shared use.

Multiprocessor system includes operating system for notifying only those

A computer-implemented method for the name-oriented accessing of files having at least zero records, any access path to files and records through an external store coupling the computer being defined by a pair of related directories. A first directory of record entries is sorted on a two-part token. The token consists of a unique sequence number assigned to the record and the sequence number of any parent record entry. Each record entry includes the token, file or record name, and external store address or pointer A traverse through the tokens constitutes a leaf-searchable B-tree. Rapid access to target records is by way of a name-sorted, inverted directory of names and tokens as a subset and which is reconstitutable from the first directory in the event of unavailability.

Method for dynamically expanding and rapidly accessing file directories

A method for allowing weak-searchers of a B+-tree avoid locks that serialize access to the B+-tree structure. The update technique used to achieve this ensures that the B+-tree is always in a correct state on secondary storage so that repair is not necessary after a system failure. The assumption is made that the readers will complete their reading within a specified period but sometimes will need to be restarted because they have not completed their reading within a predetermined time period.

Method for allowing weak searchers to access pointer-connected data

A method to manage the access of data or pages mapped into a very large virtual external address space through a cache without disturbing the logical view of the data and without having to assign physical or real backing store to said logical view. A data cache is used in which pages are indexed according to a logical address intermediate to their virtual address and their physical location in external storage. Pages common to two or more files are updated in place in the cache, while pages bound to only one file are shadow copied.

Method for managing a data cache using virtual external storage

A data cache in a computer operating system that dynamically adapts its size in response to competing demands for processor storage, and exploits the storage cooperatively with other operating system components. An arbiter is used to determine the appropriate size of the cache based upon competing demands for memory. The arbiter is entered cyclically and samples user's wait states. The arbiter then makes a decision to decrease or increase the size of the cache in accordance with predetermined parameters.

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Oakland, NJ, United States of America

Gerald P Bozman