Compensating resource managers

Details Compensating resource managers Compensating resource managers

1998-06-30

2003-02-25

Banankhah, Majid A. (Department: 2156)

Data processing: database and file management or data structures

Database design

Data structure types

C709S241000, C709S241000, C714S020000

Reexamination Certificate

active

06526416

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to on-line transaction processing applications, and more particularly relates to managing non transactional resources or non-compliant transactional resources in transaction management systems for on-line transaction processing applications.
BACKGROUND AND SUMMARY OF THE INVENTION
In many information processing applications, a server application running on a host or server computer in a distributed network provides processing services or methods for client applications running on terminal or workstation computers of the network which are operated by a multitude of users. Common examples of such server applications include software for processing class registrations at a university, travel reservations, money transfers and other services at a bank, and sales at a business. In these examples, the processing services provided by the server application typically maintains persistent data or “state” of class schedules, hotel reservations, account balances, order shipments, payments, or inventory for actions initiated by the individual users at their respective stations, such as in a database or other proprietary format data store.
Often, server applications require coordinating activities on multiple computers, by separate processes on one computer, and even within a sin process. For example, a money transfer operation in a banking application may involve updates to account information held in separate databases that reside on separate computers that may be geographically remote. Desirably, groups of activities that form parts of an operation are coordinated so as to take effect as a single indivisible unit of work, commonly referred to as a transaction. In many applications, performing sets of activities as a transaction becomes a business necessity. For example;, if only one account is updated in a money transfer operation due to a system failure, the bank in effect creates or destroys money.
A transaction is a collection of actions that conform to a set of properties (referred to as the “ACID” properties) which include atomicity, consistence isolation, and durability. Atomicity means that all activities in a transaction either take effect together as a unit, or all fail. Consistency means that after a transaction executes, the system is left in a stable or correct state (i.e., if giving effect to the activities in a transaction would not result in a correct stable state, the system is returned to its initial pre-transaction state). Isolation means the transaction is not affected by any other concurrently executing transactions (accesses by transactions to shared resources are serialized, and changes to shared resources are not visible outside the transaction until the transaction completes). Durability means that the effects of a transaction are permanent and survive system failures. For additional background information on transaction processing, see, inter alia, Jim Gray and Andreas Reuter,
Transaction Processing Concepts, and Techniques
, Morgan Kaufmann, 1993.
Prior patent applications also assigned to the assignee of the current invention (namely, Helland et al., “Automatic Transaction Processing Of Component-Based Server Applications,” U.S. patent application Ser. No. 08/959,141; and Helland et al., “Disabling And Enabling Transaction Committal In Transactional Application Components,” U.S. patent application Ser. No. 08/959,142, both filed Oct. 28, 1997; which the present application hereby incorporates by reference and hereafter refers to collectively as the “incorporated MTS Patent Applications”) disclose an execution e,environment and platform for distributed server applications, which is embodied in the Microsoft Transaction Server (MTS) version 1.0 product. MTS provides a component-based framework or object model with system services to support transactions by potentially distributed groups of components of server applications under control of a transaction manager, such as the Microsoft Distributed Transaction Coordinator (MS DTC).
In the MTS, server applications use resource managers to maintain the durable state of the application, such as the record of inventory on hand, pending orders, and accounts receivable. Resource managers are a system service that manages durable data, such as may be contained in databases, durable message queues, file systems or other data storage resources. One example is the resource manager provided with the Microsoft SQL Server version 6.5. Resource managers operate in cooperation with the transaction manager to enforce the ACID properties on the durable data of the managed resource.
Resource managers are difficult to develop and implement for a particular resource (e.g., durable data store). This is because a resource manager deals with a number of the more complex issues in transaction processing. Specifically, the resource manager must properly interface with the transaction manager, and guarantee that all operations requested to be done by components on the managed resource adhere to the ACID transactional properties. The resource manager thus must ensure that all updates to the durable data by components that are completed under a specific transaction are made durable when the transaction commits, or are rolled back if the transaction aborts. The resource manager employs transaction-based synchronization protocols to isolate uncommitted work of active transactions. The resource manager also must ensure thread safety, which means the resource manager must be capable of being called by application components from any thread. The resource manager must further provide logging and recovery so that transactions involving the resource are durable over crashes and other failures (communications failures, process failures, and storage medium failures, as well as server system failures).
Further, an MTS Resource Manager (a resource manager that has been written to support MTS) must meet some additional requirements. In particular, an MTS Resource Manager implements all (or a substantial subset) of the “OLE Transactions” interfaces, which allow integration into MTS and interface to the MS DTC. Additionally, an MTS Resource Manager must provide a resource dispenser (a service that provides pooling and automatic transaction enlistment for MTS server application components) for their managed resource. If there is no Resource Dispenser, then an alternative mechanism for automatic transaction enlistment must be provided.
Due to these difficulties, few resource managers are yet available for MTS (the Microsoft SQL Server version 6.5 previously mentioned being one example). However, a wide variety of resources with no transaction support are currently available on the market, and deployed in use. Further, there are a variety of resource managers (herein referred to as legacy resource managers) for other transactional systems that don't provide the required interfaces (i.e., the OLE transactions interfaces) to interoperate in MTS, such as to interface to the MS DTC. For example, a number of travel industry reservations systems have reservations databases managed under the IBM CICS transactional system. It is therefore desirable to integrate such non-transactional resources and legacy resource managers into MTS more easily than implementing an MTS resource manager specific to each.
The present invention provides a form of resource management (herein referred to as “compensation” or “compensating resource management”) that allows durable resources to be more easily integrated into a transactional system, and particularly into a component-based on-line transaction processing application environment such as MTS. In compensating resource management, a durable resource is integrated to participate in transactions under the transactional system by providing a compensating action to reverse each normal action performed on the resource gas part of a transaction. The normal action is persisted on the resource at the time of request. In a case where the transaction aborts, the compensating

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