International Business Machines Corporation

Anthony Cocchi

Stephen P Morgan

Marion Lee Blount

Mark F Mergen

Stephen Edwin Smith

Hung-yang Chang

Katalin A Rader

Janice Cynthia Shepherd

A method is provided for tracking the type of at least one local variable after calling a subroutine. The exemplary method associates each one of a plurality of branch instructions calling the subroutine with a first information, which indicates the type of value stored in the local variable when each one of the plurality of branch instructions is executed. The exemplary method associates at least one execution point-of-interest within the subroutine with a second information. The execution point-of-interest is any point within the subroutine where it may be necessary to ascertain the type of each local variable. The second information is a data structure indicating a change in type made to the local variable after entering the subroutine and before the execution point-of-interest. The exemplary method associates the execution point-of-interest with a return address for the subroutine. This return address enables the method to identify the point in the calling program from which the current subroutine was called. When a request is received to identify the type of the local variable at the execution point-of-interest in the subroutine, the exemplary method obtains a second map from the second information using the execution point-of-interest. The second map indicates the change in type of the local variable made within the subroutine. The method also obtains the return address associated with the execution point-of-interest, and obtains a first map from the first information using the return address. The first map indicates the type of value stored in the local variable when one of the branch instructions is executed to call the subroutine. Given the first and second maps, the exemplary method merges the first map with the second map to identify a current type for the local variable. In performing this merge, the method combines the type status of the local variable as modified by the subroutine with the type status of the local variable as it stood before calling the subroutine.

Determination of local variable type and precision in the presence of subroutines

The invention provides a method for compacting transactions which have committed at a disconnected client prior to sending the transactions to the server for replaying along with an iterative process for re-calculating the combined transaction in the event that replay at the server fails.

Transaction compaction for replay of transactions from client to server

A method for maintaining the overall system availability of a multi-processor data processing system in the event of a failure at one of a plurality of independent failure points. The system includes a plurality of virtual memory type processor units, each of which may include an interactive terminal, and a main memory which has access to a secondary storage device which is also accessible by the main memory of one of the other processor units. The two units are also directly interconnected by a communications mechanism making it possible to provide a shared virtual memory system. Both processor units employ the same operating system and share the same virtual address space for storing information. The interactive terminals are each connected to more than one processor unit. Failure points include the terminals, the processor units, the communication links, and the various software components that are employed by the system. The method maintains system availability by managing the storage of selected information at preestablished precise points in the processing operation. The method updates identical operating system data structures that are stored in each processor unit with the results of certain identified data processing transactions which have affected information required for succeeding processing operations in manner to insure that either identical updates occur or no update occurs. The method further insures that any changes that might have occurred in the information stored in the data structure prior to the end of an aborted transaction is returned to the initial state to permit the transaction to be retried whenever the path of the falilure can be bypassed.

Method for maintaining data availability after component failure

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Larchmont, NY, United States of America

Anthony Cocchi