Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-03-12
2002-10-22
Black, Thomas (Department: 2171)
Data processing: database and file management or data structures
Database design
Data structure types
C709S229000, C709S219000, C713S152000
Reexamination Certificate
active
06470342
ABSTRACT:
COPYRIGHT NOTICE
A portion of the disclosure of this patent document, referred to as “Appendix A”, contains material, titled “Transaction Internet Protocol, Version 3.0,” which is subject to copyright protection. The copyright owner has no objection to the xerographic reproduction by anyone of the patent document or the patent disclosure in the exactly the form it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
The present invention relates generally to transaction processing, and more particularly to techniques for supporting and maintaining a distributed global map of transaction identifiers at the gateway processes and using a hashing algorithm to access these maps.
A transaction is most often defined as an explicitly delimited operation, or set of related operations, that change or otherwise modify the content of an information collection (e.g., database or databases) from one consistent state to another. Changes are treated as a single unit in that all changes of a transaction are formed and made permanent (the transaction is “committed”) or none of the changes are made permanent (the transaction is “aborted”). If a failure occurs during the execution of a transaction, resulting in the transaction being aborted, whatever partial changes were made to the collection arc undone to leave it in a consistent state.
A transaction processing system typically includes a transaction manager; a collection of subsystems, called resource managers (RMs), which are essentially abstractions of available services, such as database systems; application programs; and the like. The transaction processing system provides a way to interconnect applications and resource managers while maintaining data integrity and transactional consistency.
The application process initiating a transaction invokes various services and/or resource managers to perform various operations and tasks necessary to complete the transaction. All services and resource managers invoked to perform operations for the transaction register with a transaction manager, stating that they are joining the transaction. A transaction manager typically provides transaction management functions, such as monitoring the progress of the transaction and coordinating the commit processing and rollback of the transaction, and protects the integrity of user data. When all operations, or work, have completed, the initiating application process notifies the transaction manager of this fact. The transaction manager then initiates an agreement protocol to coordinate commitment processing among all services and resource managers (including foreign transaction managers) participating in the transaction. In transaction processing the standard agreement protocol is the two-phase commitment (2PC) protocol. A description of the 2PC protocol, as well as a detailed overview of transaction processing, is presented in J. Gray et al.,
Transaction Processing Concepts and Techniques
, Morgan Kauffman, 1993, the contents of which are herein incorporated by reference.
Briefly, in phase one of the 2PC protocol, the transaction manager issues a request prepare signal to each participant (i.e., the transaction manager asks each participating service or resource manager if it believes the operations it performed to be a consistent and complete transformation). If any participant votes no, the commit fails and the transaction is aborted and rolled back; if all participating resource managers vote yes (ready to commit), the transaction is a correct transformation and phase two commences. In phase two of the 2PC protocol, the transaction manager issues a commit request signal informing each participant that the transaction is complete, and records this fact in the transaction's log. After all participants acknowledge the commit request, the transaction manager records this fact and forgets about the transaction.
Recently, a Transaction Internet Protocol (TIP) that uses the 2PC paradigm has been proposed by the Internet Engineering Task Force (IETF). Attached hereto, as Appendix A, is the final version of the IETF paper describing TIP and its requirements. The IETF paper describes a simple 2PC protocol applicable to transactions involving resources in a distributed, Internet-connected transaction. Basically, two models are described: a “Push” model and “Pull” model.
In the Push model, an application on a first transaction processing system requests that the transaction manager of that system “export” a transaction, T1, to a second transaction monitoring system to perform some work on behalf of the application. The transaction manager of the first system “pushes” transaction T1 to the second system by sending a message to the transaction manager of the second system. The message requests that the second system start a local transaction associated with transaction T1 as a subordinate of the first system, and return the name, for example “LT1”, for that local transaction branch on the second system together with the Internet address of the local transaction branch. The transaction manager forwards to the application the name, LT1, and the internet address of the transaction on the second system associated with transaction T1. The application then sends a message to the desired application on the second system, asking it to “do some work, and make it part of the transaction that your transaction manager already knows of by the name of LT1.” Additionally, the first and second transaction managers each update their own global map by associating the global transaction T1 initiated on the first system with the exported transaction branch LT1. The global map is a data structure that each transaction manager maintains in order to associate any and all remote transaction branches, such as LT1, with associated global transactions, such as T1. Because the first system's transaction manager knows that it sent the transaction to the second system's transaction manager, the first system's transaction manager knows to involve the second system's transaction manager in the 2PC process.
In the Pull model, an application on the first system merely sends a message to an application on the second system, requesting that it “do some work, and make it part of a transaction that my transaction manager knows by the name of T1.” The application on the second system then requests that its transaction manager enlist in the transaction T1. The second system's transaction manager “pulls” transaction T1 over from the first system and then initiates a local transaction, LT1, associated with transaction T1. Also, both transaction managers update their global maps. As a result of the pull, the first system's transaction manager knows to involve the second system's transaction manager in the 2PC process.
In both the Push model and the Pull model, an application on the first system communicates with the second system via a gateway process. In some cases where there is only one gateway process associated with the transaction manager, many applications resident on the transaction system may attempt to communicate with other systems through the single gateway process. This may result in a bottleneck at the gateway, thereby degrading system performance. It is thus desirable to include multiple gateways to enhance system performance. When multiple gateways are used, if a second application desires to export a transaction branch (push or pull) associated with the transaction (T1) to the second system, the transaction manager must check the global map to determine whether transaction T1 has been exported to the second system. If so, the transaction manager returns the local transaction identifier, here LT1, to the application and the application then communicates with the second system. Although this guarantees that the same transaction will never be exported twice to the same remote node, the process requires checking the global map in the transaction manager.
SUMMARY
Gondi Albert C.
Hansen Roger J.
Joshi Sameer
Klein Johannes
Lanka Sitaram V.
Black Thomas
Chen Te Yu
Oppenheimer Wolff & Donnelly
Sherry Leah
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