International Business Machines Corporation

Robert C Will

Robert Bradley Bennett

Gabriel Garcia Montero

Elias N Bayeh

Cherie C Barnes

Michael K Ainsworth

John F Harris

Frederick A Schwartz

A technique, system, and computer program for maintaining session information among multiple clustered computers for servlets and providing those servlets with various session services. The session services are implemented using a plug-in servlet engine. The session information is preferably maintained without using a persistent data store, to avoid performance penalties associated with storing information in persistent storage such as a database. A locking technique is implemented to prevent servlets from inadvertently overwriting each other's session object data. A registration process is preferably used, to optimize communication of configuration property changes. Non-proprietary interfaces are used, allowing for scalability, portability, and maximum industry acceptance of this solution.

Maintaining sessions in a clustered server environment

A computer network comprises first and second computers, each having a recovery facility for recovering a two-phase commit procedure and a recovery log. The log comprises a log name log which stores the names of other logs involved in a commit scope and a sync point log which stores sync point phase information. The log names are exchanged prior to a request for sync point. If a failure occurs during sync point, each recovery facility in the commit scope again exchanges log names to verify that there was not a log failure since the prior exchange. Absent a log failure, the logs are used to recover from the sync point failure. Communication facilities are interposed between the first and second computers and include log name exchange tables which record the previous exchanges of log names between the first and second computers. If a protected conversation is initialized from the first computer to the second computer and log names were not previously exchanged, then the communication facilities intercept the conversation and hold it until log names are exchanged.

Log name exchange for recovery of protected resources

A method and system of monitoring data structures in a computer system. A control block is established when a user obtains access to the computer system and is released when the user releases access to the computer system. A control program is provided to control operation of the computer system, and the control program has a plurality of process modules to service the control blocks. The method comprises the steps of invoking one process module to service one control block, and temporarily suspending operation of that one process module and invoking another process module to control operation of the computer system. A monitoring unit is established to indicate whether that one control block remains established. When control of the computer system is passed from the other process module back to said one process module, the monitoring unit is searched to determine whether the one control block is still established. If that control block is still established, operation of the interrupted process module is resumed; however, if the one control block is not still established, control of the computer system is passed from the one process module to the control program.

Computer system and a method of monitoring transient data structures in

Apparatus and method for communicating between a virtual machine application of a transparent services access collection and an external resource outside the collection. A second virtual machine is provided within the collection, for servicing a request to the external resource. The second virtual machine converts a VM request to CONNECT from the first virtual machine to a VTAM allocate command. An interface is provided at the collection for mapping each VM verb to a VTAM verb, for transmission over the VTAM network. The interface is bi-directional whereby VTAM commands received by a collection are mapped and converted to a VM verb and associated protocol.

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Vestal, NY, United States of America

Robert C Will