International Business Machines Corporation

James Gregory Ranweiler

Viktors Berstis

Julian Satran

Steven Jay Munroe

Alain Charles Azagury

Leon Edward Gregg

Terry Lyle Schardt

Michael James McDermott

John Michael Marberg

Danny Dolev

Glen R Mitchell

William G Kempke

Merle E Houdek

Kevin Curtis Griffin

Eugene R Jones

William C Richardson

George D Timms, Jr

Gerald John Balm

Gary F Aberle

Kuang-Chi Hu

Charles T Watson

German Goft

An apparatus, clustered computer system, program product and method utilize a unique prepare operation in connection with a resource action to effectively 'lock out' missing or inactive cluster entities such as nodes and cluster objects from rejoining a clustered computer system subsequent to the resource action. The prepare operation includes the modification of one or more cluster configuration parameters associated with a plurality of entities in a clustered computer system, such that any such cluster entity that is active during the prepare operation accepts the modifications, while any such cluster entity that is inactive during the prepare operation does not accept the modifications. By modifying cluster configuration parameters for active cluster entities, attempts by previously-inactive cluster entities to activate or rejoin clustering subsequent to resource actions will generally fail due to an incorrect or stale cluster configuration parameters for such entities, and as a result, such entities will be effectively blocked from being accepted into the clustered computer system.

Cluster resource action in clustered computer system incorporation prepare operation

In a resilient database system which includes a journaled database which is implemented at one or more locations within a distributed data processing system, multiple diverse consistency levels are specified which each detail a level of consistency to be maintained between a primary database and a replica database. A user is then permitted to select a particular level of consistency for each replica database. Thereafter, each update to a record within the primary database is utilized to initiate an update to the corresponding record within each replica database in a manner which is consistent with the selected level of consistency for that replica database. In this manner, a replica database which is fully consistent with the primary database may be provided for seamless switchover in the event of a primary database failure, while a second replica database may be provided to respond to queries by applications which do not require fully consistent data, greatly enhancing the efficiency of access to that database.

Method and system for selectable consistency level maintenance in a

In an object-based computer system, each object is contained in, and each task executes in, a protection domain. Domains exist at several hierarchical domain levels, some levels having multiple discrete domains, while others have one common domain. A task may access an object if the domain in which the task is executing is the same as the domain containing the object, or if the domain in which it is executing occupies a higher hierarchical domain level than the domain containing the object. Each object includes a domain attribute, which is a numerical value defining the domain in which it is contained. The domain attribute of the currently executing task is stored in a domain register. When an attempt is made to access data within an object, the domain attribute of the object is compared with the domain attribute stored in the domain register. If the access conditions are met, access is permitted.

Apparatus and method for controlling access to data using domains

A serialization apparatus for a data processing system wherein access restrictions are automatically enforced: (1) in behalf of individual machine instructions in order to maintain object integrity; and (2) at each user's discretion in order to maintain synchronization among all concurrent users of any given object. Various types of restrictions can be enforced in behalf of both machine instructions and users, allowing concurrent access to objects at various levels where appropriate.

Object access serialization apparatus for a data processing system

Tagged pointer handling apparatus is provided for implementation in a computer system wherein a tag bit is provided for each word in main storage. This invention provides for the mixing of data and pointers within the same storage space, and provides a capability for checking and verifying the validity of the pointers without affecting the performance or operation of other instructions. Only the tag instructions can set the tag bits ON in main storage; all other instructions store data and set the corresponding tag bits OFF. Thus, if a pointer was modified inadvertently by one of these data handling instructions, the fact that the pointer is untagged is detected and the values in the pointer are treated as invalid when the pointer is used by the Load and Verify Tags instruction. Instructions to load, store, set, move, extract and insert tags are implemented by the tagged pointer handling apparatus. A Load and Verify Tags instruction checks the validity of the pointer and if valid, loads the pointer into a specified general purpose register. A Store and Set Tags instruction stores the value in a specified general purpose register into main storage and sets the associated tag bits ON. A Move and Set Tags instruction moves a word from one location in main storage to another or the same location in main storage and sets the associated tag bits ON. A Move Characters and Tags instruction moves a word and the associated tag bits from one storage location to another storage location. An Extract Tags instruction fetches each word from an operand in main storage, extracts the tag bits, compresses the tag bits to one tag bit per quadword, and stores the tag bits in main storage as data. An Insert Tags instruction fetches the tag bits stored in main storage as data, expands the tag bits to one tag bit per word, and inserts them on each associated word of an operand in main storage.

Tagged pointer handling apparatus

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Rochester, MN, United States of America

James Gregory Ranweiler